Abstract: For improving the headway and sternway icebreaking characteristics, the hull of a ship has the greatest width of the icebreaking waterline in the forebody and has trimming and ballasting in the stern area, whose part located above the icebreaking waterline is widened to such an extent that on lowering the afterbody by trimming or ballasting during sternway travel, a channel is broken in the ice cover, which is wider than the wide forebody part passing through said channel during sternway travel.

Abstract: The method and the apparatus for removing ice from a ship's channel or from around the ship, to ease its navigation. The invention is characterized in that the propeller stream is used for removing the ice by turning the propeller stream up to the surface where the ice is. The removing influence of the stream can be further strengthened by diverting it also to the sides. Turning up the stream can be done for instance by mixing air into the propeller stream. Mechanical foils (8), for instance tilted ploughing rudders (9,10), can be used for turning the stream up and to the sides. The same air blowing apparatus can be used also for other applications, as loading the payload, or for biological aeration of water.

Abstract: An icebreaker hull having laterally projecting hull components which define inclined upwardly and rearwardly sloped faces arranged in part above and in part below the vessels normal water line, and each hull component further including a longitudinally extending face cooperating with the inclined face to define a cutting edge. At least a second pair of similar projecting hull components adjacent the first components to define a second cutting edge downstream of the first cutting edge. One or more of these hull components may be movable from and to positions where they are stowed in streamline relationship to the hull.

Abstract: For reducing the adhesive and frictional forces of snow and ice acting on the outer hull plating of an icebreaker and in particular static frictional forces when the ship becomes stuck in the ice, use is made of heating sources present and available in the hull, in order to keep warm the critical outer hull plating zones, a mixture of outside water and hot exhaust gases from the engines being ejected in the critical outer plating zone.

Abstract: An ice breaker vessel and a method for increasing maneuverability and protecting the propellers against broken ice when going backwards. The ice breaker has two stern propellers and a steering rudder aligned with each propeller shaft. Each of the rudders is individually rotatably mounted on a vertical rudder stock adjacent half the cord of the rubber blade profile length, and connected to a rudder gear, so that they e.g. may converge or diverge in the direction backwards, in abutment with end stops positioned on the stern of the ice breaker vessel, when the rudders are in their respective end positions. The method comprises turning the steering rudders in opposite directions until they cooperate and for backwards converging rudder surfaces.

Abstract: Broken ice floes move laterally by the prow of an ice breaker into a position below the unbroken ice cover laterally limit the fairway channel formed and surround the stern of the ship, so that as a result of the increased water speed produced by the propeller thrust deduction the ice is drawn into the propeller, which chops it up, so that increased propeller power is necessary. In addition, the propeller can be damaged by ice floes moved back into the fairway channel. To avoid this, the horizontal propulsion of the ice breaker takes place in propeller-independent manner by jet or rocket engines or by instantaneous or constant propulsion energy-producing force closure of the hull with a mechanical apparatus located on the ocean bed, such as a chain, cable or lowered travelling piles, and a mechanical pushing off or hauling in apparatus being provided on the hull side.

Abstract: A ship hull has a general frame form defining a bottom surface and two side surfaces. The bottom surface of the hull has a horizontal bottom section that extends longitudinally of the hull midway between the two side surfaces of the hull, and the bottom surface of the hull also has two inclined bottom sections that are located entirely below the design waterline plane and are joined to the horizontal bottom section along respective sides thereof and to the side surfaces respectively. Each join is along a clearly defined longitudinal intersection edge, whereby each side of the hull is divided into at least three clearly defined portions. The width of the horizontal bottom section and of each of the inclined bottom sections is at least 20% of the maximum beam of the hull, and the inclined bottom sections extend over a substantial part of the length of the hull.

Abstract: The stern apron is constructed as a volume body tapering to a sharp end in streamlined manner towards the stern of the ship and which at its lower outer edges is in each case wider than in the overlying region, so that the ship's resistance and the necessary propulsive power when travelling in open water is reduced and, particularly when moving astern, the propulsion and control members are protected against contact with the ice.

Abstract: A ship's hull has a general frame form defining a bottom surface and two side surfaces. The bottom section of the hull comprises a substantially vertical wedge-formed portion, which extends vertically downwards in the region of the lowest part of the bow portion of the hull. The bow portion follows in horizontal sections, at and below the design water line of the ship, a substantially continuous curved arc. The stem line of the bow extends downwards/rearwards in a small angle to the horizontal plane, in order to enable ice-breaking by means of bending.

Abstract: The invention relates to a ship that is adapted for operating in ice-filled waters and has a general frame form defining a substantially horizontal bottom surface, two side surfaces, a stern and a blow portion that breaks the ice advantageously. The bottom surface comprises one or a greater number of cavities, extending to or located on both sides of the longitudinal symmetry plane of the ship, in which cavity or cavities there are arranged movable sheetlike elements. The sheetlike elements have a first position, in which said elements form a generally continuous part of the bottom surface, and a second position, in which said elements form, below the bottom surface, a substantially vertical wedge-shaped structure that converges in the direction from the stern of the hull towards the bow of the hull. The elements are provided with power units which bring about movement of the elements from one position to another by turning around a swivelling axis arranged in the longitudinal direction of the elements.

Abstract: A mobile sea barge having a unitary lower hull which has sufficient buoyancy to float the entire barge, an upper hull spaced from the lower hull by a single, centrally-positioned, vertical member, and a movable stabilizing hull arranged about the central support member for controlled movement between the upper and lower hulls is provided. Controlled movement of the stabilizing hull permits the operational modes of submerging and emerging of the lower hull into or from a bottom-founded gravity-forced mode from which drilling operations can be carried out. In the bottom-founded mode on the sea floor the barge functions as a gravity platform. Movement of the stabilizing hull is provided by a plurality of jacking legs and jacking units which constitute the control devices. The barge can be quickly switched between the surface-floating and the gravity-forced, bottom-founded modes. Controlled vertical descent to the sea floor is provided by the static stability of the stabilizing hull.

Abstract: A vessel with a ballast system including a plurality of ballast tanks provided with means for feeding water into the tanks and expelling water therefrom and an air bubbling system including underwater openings and means for blowing air through said openings into the water surrounding said vessel. The ballast system and the air bubbling system include a common tube system being alternatively connectable to the ballast tanks, for operating the filling and emptying of the tanks, and to the air bubbling system for conducting air to the underwater openings as described in U.S. Pat. No. 3,580,204.

Abstract: A sailboat keel structure, wherein the keel has an elongated body with fore and aft edges, and a generally elliptical cross-section. An elongated slotted opening is formed along the aft edge between the upper and lower ends of the keel, with the opening extending forwardly to a point generally aft of the minor axis of the elliptically configured keel so as to create an internal chamber in the keel with an aftward opening. A plurality of bores are formed in the keel and extend diagonally from forward ports along the outer surface of the keel to aftward ports along the inner lateral surfaces of the internal chamber. While the bores may be generally cylindrical in their configuration, they are preferably tapered from a smaller diameter at the forward port to an increased diameter at the aftward port.

Abstract: A method of adding propulsive force to an ice breaker in the process of breaking ice in a frozen sea by utilizing the strong tractive force of a winch, in which a pile is first inserted in the ice, and then, a cable connected with the pile is wound up by the winch according to the advance of the ship, whereby to save fuel, and shorten the ice breaking time.

Abstract: In order to perform an ice-breaking operation more readily or with a defined geometry, an ice breaking aid is employed by virtue of which the ice is irradiated with high-frequency oscillations such as phonons or photons prior to the ice-breaking operation proper.

Abstract: A mooring and liquid transfer column which is fixed to the floor of an offshore body of water for securing a marine vessel. The column is resiliently retained and cable supported to permit its being deflected in response to ice forces acting thereagainst. The column upper end includes a narrow tower which extends beyond the water's surface and encloses fluid carrying conduits. A plurality of support cables depend from the column to transmit ice resisting forces into one or more remote anchors to which the support cables are attached.

Abstract: A floating semisubmersible off-shore drilling platform or the like comprises an upper working level portion and a lower pontoon portion. When the platform is transported from one place to another, it floats on the pontoon portion, but when it is working as a stationary unit in open water, it is submerged deeper, so that the pontoon portion is at a considerable distance below the water surface and the working level portion is at a considerable distance above the water surface. The platform is adapted to withstand ice pressure from ice occurring in the ambient water by giving the pontoon portion of the platform a form particularly advantageous in ice conditions. When ice occurs, the platform is lifted to such a position, that its pontoon portion comes to float at the water surface level.

Abstract: A method for protecting stationary constructions, located in water and surrounded by water, against strain caused by a moving ice field in said water. A protective structure is arranged around said stationary construction. Said protective structure has a cross-section considerably greater than the cross-section of said stationary construction and it comprises, at the water surface level and below this level, an outer surface which slopes downwards in a direction against the stationary construction to form an ice breaking surface bending downwards ice, which move against said protective structure.

Abstract: A vessel with a ballast system including a plurality of ballast tanks provided with pumps for feeding water into the tanks and expelling water therefrom and an air bubbling system including underwater openings and compressors for blowing air through said openings into the water surrounding said vessel. The ballast system and the air bubbling system include a common tube system being alternatively connectable to the ballast tanks, for operating the filling and emptying of the tanks, and to the air bubbling system for conducting air to the underwater openings as described in U.S. Pat. No. 3,580,204.

Abstract: An installation 18 is protected by a circular array of drag elements 2. Each drag element is anchored to the seabed and has teeth on its upper surface which penetrate, and decelerate, moving ice structures. Ice structures which move over the drag elements and enter the protection area have insufficient momentum to damage the installation.

Abstract: An ice lubrication system for easing the passage of a ship through ice laden waters. A pressurized flow of water passes through a nozzle into the inlet of a mixing chamber comprising a venturi where gas from a gas manifold is mixed with the water. The effect of the venturi is to first cause the gas to mix into the water flow and, after passage of the flow through the venturi, to cause the gas to emerge from the water. A frothy combination of gas bubbles and water is thus created which is discharged through openings in the ship's hull below the waterline. Once discharged, the gas and water combination rises up the side of the hull to provide separation and lubrication between the hull and floating ice.

Abstract: An improved method for producing an ice layer suitable for ship model ice tests on a water surface by means of a spraying process is presented. Said improvement comprises the steps of creating a low-temperature atmosphere above said water surface, forming said ice layer by spraying water freezing in said atmosphere, leading said freezing spray onto said water surface, and continuing said spraying process to form thereby the entire or at least substantially the entire ice layer on said water surface.

Abstract: An ice lubrication system for easing the passage of a ship through ice laden waters. A pressurized flow of water passes through a nozzle into the inlet of a mixing chamber comprising a venturi where gas from a gas manifold is mixed with the water. The effect of the venturi is to first cause the gas to mix into the water flow and, after passage of the flow through the venturi, to cause the gas to emerge from the water. A frothy combination of gas bubbles and water is thus created which is discharged through openings in the ship's hull below the waterline. Once discharged, the gas and water combination rises up the side of the hull to provide separation and lubrication betwen the hull and floating ice.

Abstract: A floating offshore structure which is moored at a fixed position on the sea by means of mooring hawsers and anchors connected to the ends thereof respectively for conducting a submarine excavating operation from a deck of the structure. The structure includes a moorage hull part provided with a vertical through-hole formed therein for receiving an excavating drill pipe and the mooring hawsers and a movable hull part connected to the moorage hull part so as to be rotatable within a horizontal plane. The movable hull part is constituted as a hull defining the outer wall of the floating offshore structure and connected with the moorage hull part by inserting it into a moorage hull part receiving hole formed at a position closer to the bow thereof.

Abstract: A canopy system for deployment around the periphery of a vessel floating on a body of water is disclosed primarily for use in connection with drillships in Arctic waters.

Abstract: An icebreaker hull is disclosed having cutting edges and sloping ramps that substantially surround the icebreaker's forefoot and taper as they continue aft along the sides of the hull. The cutting edges produce grooves in the underside of the ice to reduce the resistance of the ice to breaking. The ramps are used to break the ice near the bow of the icebreaker and to remove the broken pieces from the water. The pieces of broken ice move along the sloping ramps as the icebreaker continues its forward movement through the ice field. The tapered portions of the ramps provide for the broken pieces of ice to be deposited substantially in windrows on the surface of the unbroken ice field. Thereafter, sweep assemblies that extend away from the hull on both the port and starboard sides are positioned to move the windrows further away from the substantially ice-free channel that is formed behind the icebreaker as it moves forward through the ice field.

Abstract: An improved marine drilling barge for use in ice-covered water is disclosed. The barge has, besides a conventional moon pool through which conventional marine drilling operations can proceed, a roughly circular polygonal hull plan, with an elevation of two truncated pyramid sections joined through their theoretical apices by a vertical walled matching polygonal section. The flat bottom of the hull, to or through which mooring lines are attached to anchor the barge, has an exterior guard member fastened thereto and surrounding the points at which the mooring lines attach or come closest to the hull. The barge is ballasted to achieve downward breaking action by the hull on the ice cover as the latter encroaches on the barge. The proportions of the hull combine with those of the guard member to ensure that the ice broken from the ice cover is deflected to avoid fouling the mooring lines while the maximum draft of the barge is no greater than 20 meters.

Abstract: A structure for use in exploiting arctic offshore areas where floating ice masses may be present. The structure is comprised of a floating hull having ice-breaking capabilities which is moored by a plurality of mooring means which extend vertically from a moonpool in the hull to the marine bottom directly under the hull. The mooring means comprises flexible lines, e.g. nylon, steel, or the like or rigid conduits, e.g. drill pipe.Means are provided within the moonpool for tensioning the mooring means to thereby draw the hull downward to a position below its normal buoyant position thereby substantially eliminating vertical heaving of the hull. When an ice mass contacts the hull, tension on the mooring means is relaxed to thereby allow the hull to rock upward against the ice thereby generating the forces necessary for the ice-breaking operation. Due to the present mooring means, the hull moves only a relatively short lateral distance in breaking an approaching ice mass.

Abstract: A propeller mount for deflecting ice away from the propeller of an icebreaker includes a wedge-shaped body, the front end of which is pointed, and the remainder of which flares rearwardly to direct ice outwardly away from the propeller assembly. By providing bubblers in the sides of the body near the front end thereof, outward deflection of ice by the mount is promoted. The rear of the body is also slightly wedge-shaped to provide a similr wedging action at the stern for steering ice away from propellers.

Abstract: A shipborne system for clearing a channel through ice comprises in combination with a prow-mounted icebreaker shape, a giant siphon including an intake leading to an upward passage which inclines to the rear so that ice blocks taken into it at the bow float upwardly and rearwardly where they are discharged, either laterally or over the stern, leaving a broken channel behind the ship for passage of other ships; discharge provisions include underwater discharge and trap-chamber above.

Abstract: Large vessel having an opening in the bottom of the hull said hull portion being provided with an upwardly and downwardly movable grid structure shielding the opening against ice flakes which pass along the bottom of the hull.

Abstract: The disclosed method for increasing the maneuverability of a ship in ice-covered waters is comprised of bringing generally vertical ice-crushing surfaces on one side of a ship into contact with an ice covering in order to create an imbalance of forces between that side of the ship and the ice covering in comparison with the forces between the other side of the ship and the ice covering in order to assist in turning the ship. The generally vertical ice-crushing surfaces are positioned on both a starboard and port side of the hull of the ship in such a manner that they remain out of contact with the ice covering normal straight forward travel. A particular positioning mechanism is utilized in order to bring a generally vertically oriented ice-crushing wall portion into contact with the ice covering.

Abstract: Improved apparatus is disclosed for supporting the cutting teeth on the periphery of a rotating cylindrical drum ice cutter affixed to a floating arctic structure. The cutting teeth are individually removably affixed to brackets which extend spirally (either continuously or in segments) around the drum periphery and are supported in spaced relationship radially outwardly therefrom by very sturdy struts. Several benefits are obtained with this configuration: (1) hydrodynamic drag is minimized; (2) the teeth-support structure can be made more rugged than individual ones for each tooth; (3) the teeth can be configured for a minimum of replaceable material at the cutting tips; (4) more free volume is available around the drum periphery for disposal flow of disaggregated material and (5) tooth spacing can be readily adjusted for optimum performance according to requirements.

Abstract: A skirt system is disclosed in combination with a barge floating on a body of water, the barge having a roof extending over the body of water, for providing a substantial ice-free zone around a barge out to at least a hundred feet from the barge.

Abstract: A navigation channel is made in the ice covering the surface of a waterway by propelling a vessel so that its bow breaks the ice to form a channel having a width of the beam of the ship and an auxiliary channel is similarly formed at each side of the ship in rear of its bow to provide leeway for the ship to turn. As the ship is turned, the auxiliary channel is enlarged by breaking the ice on the edge of the auxiliary channel toward the stern of the ship to give it greater leeway to turn. The auxiliary channel may be broken out by fin means projecting from the side of the ship effective to exert forward, upward and outward force against the ice blanket to break pieces from it.

Abstract: A novel barge construction is disclosed herein for providing a substantially ice-free zone around a vessel out to at least 100 feet from the vessel. The barge comprises: (a) a hull including a bow, a stern and, a pair of sides, a flat bottom all covered by plating and a deck covered by decking; (b) a hull stabilization system including a lattice framework filled with solid insulation material; (c) a liquid/gas heat exchange system within the hull, such heat exchange system having ducts and outlets therefrom from the hull to project hot gas towards the surface of the water and recirculation inflow structure to recover air and hot gas from the region of the surface of the water; (d) a cantilevered section extending forwardly from the bow and including longitudinally extending skirt ducts therein connected to the heat exchange system ducts and outlets; and (e) a skirt suspended from the forward edge of the cantilevered section to below the waterline of the barge.

Abstract: An apparatus and method are provided for agitating liquids, maintaining solids in suspension and breaking up surface ice on waterways is provided in which a base plate having a plurality of dependent probes adapted to be immersed in a liquid to be agitated in subject to vibratory energy produced by selectively rotating eccentric weights in a vibratory case fixed on top of said base plate.

Abstract: An offshore structure which is able to withstand the ice forces imposed thereon by impinging ice sheets and other larger masses of ice wherein the structure has an upper conical portion coaxially positioned relative to a lower conical portion. The walls forming both the upper and lower portions are inclined at an angle to the horizontal to receive ice masses moving into contact with the structure. The angle of inclination from the horizontal of the upper portion is greater than the angle of inclination of the lower portion, and the cross-sectional diameter of the upper conical portion is no greater than that at the top of the lower conical portion.

Abstract: An offshore structure which is able to withstand the ice forces imposed thereon by impinging ice sheets and other larger masses of ice wherein the structure has an upper conical portion coaxially positioned relative to a lower conical portion. The walls forming both the upper and lower portions are inclined at an angle to the horizontal to receive ice masses moving into contact with the structure. The angle of inclination from the horizontal of the upper portion is greater than the angle of inclination of the lower portion, and the cross-sectional diameter of the upper conical portion is less than that at the top of the lower conical portion so that there exists a step-like section between the upper conical portion and the lower conical portion.

Abstract: An air cushion vehicle has a plurality of webs extending out between adjacent skirt members, with a solid or tubular peripheral member attached to the web members at their forward parts. The web members and the peripheral member guard the skirt against damage by debris, such as ice. The webs tend to ride up over an ice edge, while ice floes or similar objects are deflected by the peripheral member. The peripheral member can be in the form of a blade to cut off humps of ice on the top of an ice sheet or floe.

Abstract: The invention relates to a water navigable vessel having an ice-breaking bow and a rotatable screw mounted on the front on the bow for the purpose of advancing the vessel up onto an ice layer and failing the ice layer in flexural bending. The rotatable screw includes ice-cutting blades which form grooves within the top of said ice layer thus translating the rotational energy of said screw into a generally horizontal, (longitudinal) tractional force which pulls or drags the bow of said vessel forward and over said ice layer and, thereby, utilizes the mass of said bow to impart a downward gravitational force upon said layer of ice to cause it to fail flexurally.

Abstract: A heat transfer method for melting thick layers of ice advancing toward an object facing the ice is disclosed. Elongated grooves or corrugations are disposed in the exterior surface of the object facing the ice. A heating fluid is circulated in intimate contact with the inside of the grooved surface, and a force is maintained between the grooved surface and the advancing ice layer. The grooves increase the heat transfer rate to the ice both by increasing the surface area exposed to the ice and by providing channels for controlling the flow of the melted ice liquid to initiate and maintain a forced convection mode of heat transfer that is necessary for high ice-melting rates. A preferred application of the invention is in oil and gas exploration and production in Arctic regions where moving ice sheets must be melted to maintain a drilling platform or oil production platform positioned over a submerged well site during periods when moving ice fields overlie the well site.

Abstract: A stationary offshore platform is protected against damage from moving ice sheets by a conical shield surrounding the platform support structure and having means, such as a pneumatic biasing system, for raising or lowering the shield along the platform support. A system of mooring lines, thrustors, or the like is used to rotate the shield about the platform support. After an advancing ice sheet contacts the narrower upper portion of the shield, the shield is raised so that a wider lower portion of the shield can exert an upward force on the ice sheet to break the ice into pieces. The shield is rotated, while in its elevated position, to carry the broken ice with it to a location downstream from the advancing ice sheet. The shield is then lowered to dump back into the ocean the ice pieces broken by the upstroke of the shield. Means are provided for heating the exterior surfaces of the shield to melt ice pieces sticking to it.

Abstract: Ice is broken with expenditure of less energy by pumping water from beneath the ice and discharging it in large quantities onto the surface of the ice. Breaking stress is provided by the weight of the water and by thermal shock. A conventional ice breaking apparatus can also be run up onto the ice to provide a breaking force in which case friction between the ice and the ice breaking apparatus is lessened by the water.

Abstract: An arctic drilling barge to perform offshore activities in the shallow water, fast ice regions of the arctic seas. Optimal ice interaction is obtained by shaping the hull of the barge in the form of an upright frustum. Ice which does adhere to the barge is detached and melted by circulating fluid through a plurality of interior hull compartments next to the hull sidewalls of the barge.

Abstract: A heat transfer system for melting thick layers of ice advancing toward an object facing the ice are disclosed. Elongated grooves or corrugations are disposed in the exterior surface of the object facing the ice. A heating fluid is circulated in intimate contact with the inside of the grooved surface, and a force is maintained between the grooved surface and the advancing ice layer. The grooves increase the heat transfer rate to the ice both by increasing the surface area exposed to the ice and by providing channels for controlling the flow of the melted ice liquid to initiate and maintain a forced convection mode of heat transfer that is necessary for high ice-melting rates. A preferred application of the invention is in oil and gas exploration and production in Arctic regions where moving ice sheets must be melted to maintain a drilling platform or oil production platform positioned over a submerged well site during periods when moving ice fields overlie the well site.

Abstract: An ice removal system to protect a drill string in an ice covered waterway from possible damage due to ice movement. The drill string extends down into the waterway from a vessel which has an ice melting system for melting ice coming into direct contact with it. If the ice is thicker than the draft of the vessel, the unmelted portion of the ice passing under the vessel is deflected downward by ice breaking ridges surrounding the drill string. The downward deflection causes the ice to fail in tension thereby breaking it up into a plurality of ice blocks. The ice blocks float up into a moon pool surrounding the drill string, and are then flushed out of the moon pool through a channel and into the surrounding waterway. A cylindrical protective plate surrounding the drill string prevents the ice blocks from coming into direct contact with the drill string and thereby possibly damaging it.

Abstract: A method of deflecting ice for protecting upright legs of stationary or floating marine structures such as marine offshore drilling platforms or the like against drift ice by suspending a heavy mass along the leg of the structure in the vicinity of the water surface and oscillating this mass so that the oscillating mass periodically hits ice adjacent the leg of the structure whereby the oscillations of the mass are generated within the oscillating mass and the resultants of the active and reactive forces and the center of gravity of a semi-cross-sectional area of the oscillating mass substantially coincide along a vertical line spaced from and substantially parallel to the leg of the structure. The ice deflector assembly includes an annular or U-shaped oscillating body suspended about the leg of the protected structure, the body housing internal oscillation generating means for generating vertical and/or horizontal oscillations of the body.

Abstract: An offshore structure, adapted for operation in an ice infested arctic environment, includes a floating caisson that can be actively heaved in the water to break ice. The caisson comprises a radially tapered upper portion, preferably conically shaped. Means for vertically moving the caisson are provided so that the upper portion of the caisson can obliquely contact ice sheets and other ice masses with sufficient dynamic force to pierce and break the ice. A plurality of mooring lines anchored to the sea floor are attached to the caisson to secure its position in the water.

Abstract: The invention relates to the generation of compressed gas for bubbling from a ship's hulls in ice-laden water in order to reduce the drag on the ship's movement produced by the ice, and also to help break up the ice. The compressed gas is generated by apparatus having an air compressor, a device for mixing fuel with the compressed air, a device for igniting the fuel/air mixture so that hot gas is generated under pressure, and at least one pipe which is provided for receiving the hot compressed gas and for supplying the gas to holes located in the hull of the ship below the waterline. The pressure of the gas is greater than the water pressure at the holes so that bubbling of the gas from the holes takes place.