A power transmission device is configured to transmit power underwater to an underwater vehicle having a power reception coil. The power transmission device includes a power transmission coil configured to transmit power to the power reception coil through a magnetic field, a power transmission unit configured to transmit an alternating current voltage having a frequency a 10 kHz or lower to the power transmission coil, and a first capacitor connected to the power transmission coil and configured to form a resonance circuit resonating at the frequency with the power transmission coil.

An electricity generating system includes a first electrode located at a first location in a body of salt water and a second electrode located at a second location in the body of salt water. The first and second electrodes may be of the same or different materials and are designed to present a large surface area to the body of water. A direct current flows between the two electrodes which is a function of the salinity of the water and the composition of the electrodes. The direct current is applied to the input port of a converting device which may be any suitable power inverter which can produce a output AC voltage corresponding to the direct current or a DC to DC converter to produce an output DC voltage corresponding to the direct current.

An electricity generating system includes a first electrode located at a first location in a body of salt water and a second electrode located at a second location in the body of salt water. The first and second electrodes may be of the same or different materials and are designed to present a large surface area to the body of water. A direct current flows between the two electrodes which is a function of the salinity of the water and the composition of the electrodes. The direct current is applied to the input port of a converting device which may be any suitable power inverter which can produce a output AC voltage corresponding to the direct current or a DC to DC converter to produce an output DC voltage corresponding to the direct current.

A drive module for submersible autonomous vehicles is disclosed. The drive module includes a propulsion element configured to engage and rotate against a surface, a motor configured to drive the propulsion element, and a controller configured to cause the motor to drive the propulsion element. The drive module also includes a housing configured to be removably, releasably coupled to the exterior of a submersible autonomous vehicle. The motor and the controller are disposed within the housing.

An underwater propulsion device is disclosed comprising two sleeves for fitting around each of a user's lower legs, with each sleeve mounting a propulsion unit, and the sleeves being connectable by a bar between them during underwater operation of the device by the user.

An underwater propulsion device is disclosed comprising two sleeves for fitting around each of a user's lower legs, with each sleeve mounting a propulsion unit, and the sleeves being connectable by a bar between them during underwater operation of the device by the user.

An underwater propulsion device is disclosed comprising two sleeves for fitting around each of a user's lower legs, with each sleeve mounting a propulsion unit, and the sleeves being connectable by a bar between them during underwater operation of the device by the user.

An underwater propulsion device is disclosed comprising two sleeves for fitting around each of a user's lower legs, with each sleeve mounting a propulsion unit, and the sleeves being connectable by a bar between them during underwater operation of the device by the user.

The invention relates to a vessel for operating on a body of water comprising: a non-planing hull having a waterline and a longitudinal direction with a forward portion, an aft portion, and a central portion, the hull being configured to have the aft portion with a smaller water displacement relative to a water displacement at the central portion; and an aft foil affixed to the aft hull portion with one or more connecting members, and below the surface of the water, and spaced from the hull, the aft foil having a span, a chord, and a leading edge and a trailing edge relative to a forward direction, wherein the leading edge of the aft foil is tilted at a downward angle relative to the horizontal, wherein the aft foil has a chord and profile in longitudinal cross section, with a configuration to provide a lifting force, the tilt angle of the chord of the aft foil being measured with respect to the horizontal, and wherein the aft foil is oriented to provide a continuous, upward, forwardly directed component of the lifting force.

An apparatus includes first and second tanks each configured to receive and store a refrigerant under pressure. The apparatus also includes at least one generator configured to receive flows of the refrigerant between the tanks and to generate electrical power based on the flows of the refrigerant. The apparatus further includes first and second hydraulic drives associated with the first and second tanks, respectively. Each hydraulic drive includes a first piston within the associated tank, a channel fluidly coupled to the associated tank and configured to contain hydraulic fluid, and a second piston within the channel and configured to move within the channel in order to vary an amount of the hydraulic fluid within the associated tank and vary a position of the first piston within the associated tank. The channel of each hydraulic drive has a cross-sectional area that is less than a cross-sectional area of the associated tank.