1-17. In most situations, the delivery of swimmers by parachute during periods of limited or reduced visibility onto unmarked water drop zones (DZs) requires the use of the computed air release point (CARP). Parachutists exit the aircraft on the pilot’s command at a point designated by the navigator, and attempt to group in the air as close as possible. Once in the water, they sink their air items and sterilize the DZ by sinking everything to ensure that nothing floats ashore. The detachment then begins movement to the BLS or launch point.