The crotch strap helps maintain the position of the equipment. When swimming in a vertical position, such as during descent along the anchor line, the crotch strap prevents the tanks from moving towards the diver's shoulders. This is especially useful when using double tanks. When the diver is on the surface, the crotch strap prevents the equipment from rising onto the diver's body. Crotch straps are also used during scooter dives. The scooter strap is attached to a "D" ring in front of the crotch strap (DIR style). This technique helps reduce arm fatigue during long scooter dives.