The invention relates to a water tank cleaning machine used in cleaning operation of water tank such as aquarium, swimming pool and bathtub, characterized by rotating a suction impeller pivoted on a second suction chamber by rotating device, sucking storage water in the water tank through each suction port formed in first suction chamber and second suction chamber, transmitting the torque of the rotating device to wiping device through power transmission device, and stopping the wiping device only due to resistance caused at the time of contact if a hand of the worker or aquatic creature or other object contacts with the wiping device, thereby preventing injury of the object, so that it is easy to handle and safe, and moreover, since the water tank is cleaned while filtering the storage water, contamination of storage water during cleaning work is prevented, and the water quality and environments suited to rearing of aquatic life such as fishes and mammals can be maintained, and further, since the water tank can be cleaned while holding the storage water therein, the labor of discharging or replacing storage water is omitted, and the inner wall and deposits of the water tank can be cleaned easily, thereby enhancing the working efficiency and cleaning efficiency.

A vortex generating apparatus has the capability of attracting and removably adhering one or more solid objects. The apparatus comprises an impeller housed within a shell. The vortex attractor generates a vortical fluid flow generally in the form of a helical or spiral shaped flow. The fluid flow creates a low pressure region extending from the impeller end of the device. This low pressure region is contained by the walls of the fluid flow, thus directing the attractive forces toward a surface and minimizing effects of ambient fluid on the system. When the surface is part of a stationary object, wall, floor or ceiling, the vortex attractor may move toward and adhere to the surface. When the surface is part of a movable object, the vortex attractor may attract the object and maintain the attracted position.

A vortex generating apparatus has the capability of attracting and removably adhering one or more solid objects. The apparatus comprises an impeller housed within a shell. The vortex attractor generates a vortical fluid flow generally in the form of a helical or spiral shaped flow. The fluid flow creates a low pressure region extending from the impeller end of the device. This low pressure region is contained by the walls of the fluid flow, thus directing the attractive forces toward a surface and minimizing effects of ambient fluid on the system. When the surface is part of a stationary object, wall, floor or ceiling, the vortex attractor may move toward and adhere to the surface. When the surface is part of a movable object, the vortex attractor may attract the object and maintain the attracted position.

A system for producing hydrogen from water, making use of a stream of water such as a gulf stream or tidal stream, includes a number of submerged modules, each having a turbine that can be driven by the stream of water. The turbine is coupled to a generator for generating electrical energy. Each module may have submerged decomposition means for decomposing water into hydrogen and oxygen using the electrical energy generated. The modules are provided with means to control the depth of the modules below water level, and furthermore with means for automatically orienting the front of the modules--viewed in the longitudinal direction of the turbines--to the direction of flow of the water or an angular position deviating therefrom.