Abstract: An improved diving snorkel for increasing the effectiveness of water purging and for decreasing the likelihood of water interference with breathing, and for reducing the breathing resistance, utilizes one or more of the following features: A trough in the partition between the breathing tube and the purge conduit using a hole to drain water and prevent backflow even when the diver rotates his head; a rise or deflector on the mouthpiece side of the partition to resist water flow toward the mouthpiece and promote drainage through a hole in the partition; a Venturi-type construction in the breathing tube to increase water purgin efficiency for a given exhalation effort; as well as decrease the resistance to air flow to the user; and an air trap immediately exterior to the purge valve in the branch conduit for reducing the resistance to opening of the valve thus promoting easier drainage of residual water in the branch conduit.

Abstract: A hydrodynamic swim fin utilizes a wing and a tail that are overlapped normally to provide a two stage propulsion system. Ribs support the wing and tail and define flow channels. These ribs are parallel to each other and to the longitudinal axis of the fin whereby the effective area through which flow proceeds is uniform throughout the length of the fin. No parts of the ribs form barriers to the leading edges of the side wing segments whereby laminar flow is achieved. The fin part is maintained essentially rigid; however, the fin part is allowed limited angular movement about a defined transverse axis to achieve proper attack angle. Since the fin part is rigid, it maintains that attack angle throughout the length of the fin part. Trailing ends of the wing are individually flexible to produce greater opening for two stage propulsion during the power downstroke, and to produce substantial closure for one stage propulsion during the upstroke.

Abstract: An improved hydrodynamic swim fin utilizes a wing and a tail that are overlapped normally to provide a two-stage propulsion system. Ribs support the wing and tail and define flow channels. These ribs are parallel to each other and to the longitudinal axis of the fin whereby the effective area through which flow proceeds is uniform throughout the length of the fin. No parts of the ribs form barriers to the leading edges of the side wing segments whereby laminar flow is achieved. The fin part is maintained essentially rigid; however, the fin part is allowed limited angular movement about a defined transverse axis to achieve proper attack angle. Since the fin part is rigid, it maintains that attack angle throughout the length of the fin part. Trailing ends of the wing are individually flexible to produce greater opening for two-stage propulsion during the power downstroke, and to produce substantial closure for one-stage propulsion during the upstroke.