FIG. 3.

P-valves can be unbalanced (A) or balanced (B). Balanced P-valves equalize the pressure between the valve system and the outside water pressure, avoiding reflux of water at high pressure. In addition, it prevents “genital squeeze” that can occur with an unbalanced system's tubing. An unbalanced P-valve also protects from water entering into the suit; however, it may allow some retroflux of ambient water into the P-valve tubing system at extreme depths. P-valves can be installed in the upper thigh of a dry suit (C).