A backrest for a scuba diver comprising a shaped plate supporting at least one air cylinder, at least a first strap comprising an upper right portion configured to fit around the scuba diver's right shoulder, an upper left portion configured to fit around the scuba diver's left shoulder and a lower portion configured to fit around the scuba diver's abdomen, wherein the shaped plate has a first right slide-through element and a first left slide-through element adapted to connect the upper right portion and the upper left portion, respectively, to the lower portion of the first strap, at least one weight pocket constrained to the lower portion of the first strap, wherein there is provided an anti-torsion means connecting the at least one weight pocket to the shaped plate and configured to oppose the torsion of the first strap in proximity to at least one of the first slide-through elements.

A device for releasably connecting a first element with a second element includes a male element connectable to one end of the first element, and a female element connectable to one end of the second element such that the male and female element pass from a disengagement condition to a mutual engagement condition. A slider activates and deactivates engagement and is engaged to the male element such to slide along the axis of insertion of the male element inside the female element. The relative motion between the activation/deactivation slider and the male element is transmitted to first removable locking members, belonging to the male element and cooperating with corresponding second locking members belonging to the female element, such to pass from a stable locking condition to a stable release condition of the male and female elements via a movement of the slider along the axis of insertion.

A device for releasably connecting a first element with a second element includes a male element connectable to one end of the first element, and a female element connectable to one end of the second element such that the male and female element pass from a disengagement condition to a mutual engagement condition. A slider activates and deactivates engagement and is engaged to the male element such to slide along the axis of insertion of the male element inside the female element. The relative motion between the activation/deactivation slider and the male element is transmitted to first removable locking members, belonging to the male element and cooperating with corresponding second locking members belonging to the female element, such to pass from a stable locking condition to a stable release condition of the male and female elements via a movement of the slider along the axis of insertion.

An underwater recreation system for diving instruction and method of its use. The method includes providing a series of learning steps with diving techniques and instructions to practice at incrementally deeper depths and providing a surface floating depth limitation device that restricts the learning user to the particular maximum depth of their learning step. The apparatus for carrying out the method of diving instruction includes a surface floating depth limitation device with the means to connect to the breathing hose of a surface supplied air supply.

An underwater recreation system for diving instruction and method of its use. The method includes providing a series of learning steps with diving techniques and instructions to practice at incrementally deeper depths and providing a surface floating depth limitation device that restricts the learning user to the particular maximum depth of their learning step. The apparatus for carrying out the method of diving instruction includes a surface floating depth limitation device with the means to connect to the breathing hose of a surface supplied air supply.

A scuba cylinder lower side mounting system employs two mating parts to secure the lower portion of a scuba cylinder to a diver's torso, the first affixed to either side of any side-mount or back mount Buoyancy Control Device utilizing a web waistband. A web cylinder band or stainless steel hose-clamp secures the second part to any scuba cylinder. The two parts are engaged whether in or out of the water by inserting the second part into the first and pivoting the cylinder at the point of attachment. Existing arrangements to position the cylinder valve near the diver's armpit will keep the system locked in place. It may be disengaged before entering or engaged after exiting confined underwater spaces without reaching between the cylinder and diver's torso. The system keeps the cylinder close to and aligned with the diver's torso regardless of the cylinder's change in buoyancy or diver orientation.

A scuba cylinder lower side mounting system employs two mating parts to secure the lower portion of a scuba cylinder to a diver's torso, the first affixed to either side of any side-mount or back mount Buoyancy Control Device utilizing a web waistband. A web cylinder band or stainless steel hose-clamp secures the second part to any scuba cylinder. The two parts are engaged whether in or out of the water by inserting the second part into the first and pivoting the cylinder at the point of attachment. Existing arrangements to position the cylinder valve near the diver's armpit will keep the system locked in place. It may be disengaged before entering or engaged after exiting confined underwater spaces without reaching between the cylinder and diver's torso. The system keeps the cylinder close to and aligned with the diver's torso regardless of the cylinder's change in buoyancy or diver orientation.

A diving apparatus for a diver underwater includes a portable habitat in which a breathable environment is maintained underwater. The habitat has a collapsible envelope. The collapsible envelope takes shape through inflation to an expanded state underwater. The habitat has a modular payload which removably attaches to the envelope underwater. The habitat has a seat on which a diver can sit while the habitat is underwater. The modular payload has a breathable gas source to provide breathable gas for the diver to breathe in the habitat and a carbon dioxide scrubber which removes carbon dioxide from the environment when the habitat is underwater. The apparatus has an anchor mechanism attached to the habitat to maintain the habitat at a desired depth underwater. A method for a diver to dive underwater. A system for supporting a diver underwater. A diving apparatus having a propulsion unit. An apparatus for a user in outer space or on another planet.

A human-powered underwater propulsor for user's moving in water mainly has a power generating module provided within a receiving space inside a waterproof airbag, and the power generating module is coupled to a propulsion unit. The receiving space is formed with an opening end provided with a waterproof ring to be worn by user in such a manner that the receiving space is hermetically sealed to prevent water from entering the receiving space during diving. When user pedals by stepping on two pedals of the power generating module, the power generating module is actuated to cause the flapping of the propulsion unit. Hence, the human-powered underwater propulsor allows user to exercise his feet in the air to reduce drag in diving so that user can moves more easily in the water.

The invention relates to a free diving weight belt including a belt with a buckle that supports attaching a variety of accessories and/or a knob-back screw fastener that can be used to reconfiguring the belt. It permits attaching a variety of screw-on attachments, including but not limited to clips, knives, snorkels, weights, D-rings, weight keepers, and knife holders. It also provides the knob-back screw fasteners to secure excess belt extending beyond the buckle and/or hassle-free attachment of accessories.