Abstract: The propulsion system includes a series of large inclined propellers which operate like the wheels of a vehicle and have the functions of lifting, propelling and steering the boat on the water.

Abstract: A decompression meter includes a scale having a first section corresponding to conditions in which it is unnecessary for an ascending diver to carry out decompression halts, and a second section corresponding to conditions in which decompression halts are necessary. The second section of the scale is carried by a movable element which can be displaced along the first scale section by means of a manually operable member. Means are provided for indicating the position of the movable element along the first scale section. The position in which the movable element is set is selected by the diver at least on the basis of the maximum depth reached and, optionally, also on the basis of the dwell time at this maximum depth as well as possibly also on the basis of the intervening time between a preceding dive and the current dive.

Abstract: A depth gauge, of the type having a dial with a graduated scale over which an indicator needle is movable by a manometer unit housed in a capsule filled with liquid which communicates ambient pressure to a pressure-sensitive element of the manometer, in which there are provided calibration means for adjusting the pressure within the capsule with respect to the external ambient pressure in order to adjust the needle setting to zero immediately prior to use. The capsule may have one or two flexible walls and the calibration means include a screw threaded element, which may be part of a casing for the capsule or may be screwed into a part of this casing, which engages the resiliently flexible wall and causes flexure of it one way or the other when screwed in one direction or the other, to increase or reduce the pressure in the liquid filling the capsule with respect to the external ambient pressure.

Abstract: A device for indicating the maximum reading of a measuring instrument of the type having a needle turnable over a dial marked with a graduated scale extending for more than 360.degree. includes an auxiliary needle mounted on a pivot pin carried by a transparent screen covering the dial and lightly frictionally engaged with this pin so that it can be turned, for zero setting, by rotation of the pin by means of a knob attached to the outer end thereof. The auxiliary needle is provided with engagement means by which it is engaged by the main needle upon advancing movement, but which allows the main needle to pass the auxiliary needle should it require to do so, having reached a maximum position more than 360.degree. from the zero of the scale so that, upon returning to zero, it passes the auxiliary needle which remains fixed at the maximum position reached.

Abstract: A fluid pressure transducer has a sealed capsule with a thin bellows wall of flexible plastics material and rigid end walls attached to a support and to an indicator respectively, so that longitudinal expansion and contraction of the capsule due to variation of the pressure of the fluid in which the capsule is immersed give an indication of this pressure. The capsule contains a gas which imparts an effective elasticity to the capsule, the elasticity of the bellows wall itself being negligible, so that the length of the capsule is to a close approximation inversely proportional to the applied pressure. For direct pressure measurement the floating end of the capsule may carry an indicator which is visible through a wall of a rigid capsule-enclosing casing to which the pressure to be measured is applied.

Abstract: An instrument for indicating the depths and durations of the decompression stops required to be made by a diver during an ascent from an underwater dive is disclosed. The instrument comprises a transparent rigid cylindrical chamber linked to a chamber having at least one resilient wall by a restrictor which allows only a very slow transfer of gas from one chamber to the other. Within the rigid chamber is a pressure indicator comprising a transparent or semi-transparent pipe one end of which is sealed and the other end of which is open to the interior of the rigid chamber. A piston is slidably housed in the pipe and moves along it in dependence on the pressure in the rigid chamber, the position of the piston forming a visible indication of the pressure.