Abstract: Watercraft structure, in particular an aquabike, comprising a first elongated floating body (5) and a second elongated floating body (6) connected to the first floating body and arranged parallel to it spaced at a determined distance. Between two floating bodies (5, 6), furthermore, a seat (16) is provided, which can be associated to a footrest and is connected by a rod (26) to the floating bodies (5, 6), on which one or more users can sit. For increasing the lifting forces pushing against the floating bodies (5, 6), a hydrodynamic lifting transversal element (30) is provided arranged at the barycentre of the watercraft (101). The hydrodynamic lifting transversal element (30) in use has an upper surface (31) that faces the floating bodies (5, 6) and a lower surface (32) opposite to the upper surface (31).

Abstract: A lifting device (10) for watercrafts of the fully planing or semiplaning type provides at least a transversal element (15) constrained to the bottom (25) by means of supports orthogonal to the waterline (8) and suitable to increase the hydrodynamic lift acting on the bottom (25). The position of the device (10) may be under the barycentre (5) or slightly shifted from it, and generates, when in navigation at a sufficient speed (4), an additional hydrodynamic lift (6), which adds to the hydrodynamic lift (3) on the bottom and to the hydrostatic lift (2) for balancing the weight of the watercraft. The transversal element (15) is arranged substantially parallel to the watercraft bottom (25), so that in fully planing or semi-planing conditions it is inclined with respect to the speed (4) of the watercraft. This way it is possible to reduce the amount of water displaced during navigation and to supply a steady hydrodynamic lift.

Abstract: Retractable auxiliary and emergency propulsion device for small craft comprising a hydraulic motor with its own propellor, powered by a hydraulic pump applied either to a motor installed on the craft just for this purpose and of considerably reduced power compared to the principle motor or to other motors already on the boat for other purposes, such as, for generators, refrigerators, compressors and the like the hydraulic motor sliding on inclined guides placed in the stern of the craft so as to be dropped into the sea when necessary, or raised up and placed in a suitable storage space in the boat.