Drift diving is a method of open water scuba diving required where current is at or greater than one knot. It is the recommended mode of diving if there is any current at all. As the name states the diver drifts with the current while submerged. When the divers leave the boat the boat simply cuts the engine and drifts along above and with the divers. The divers end up surfacing within 100 yards from the boat. Dive masters signal pickups by inflating a day-glo orange sausage shaped balloon or bubbling a large volume of air by hitting the purge on the regulator for several seconds.
This is a relatively easy method of diving as it requires minimal finning and thus minimizes air consumption rates as the diver is not exerting themselves. Bouyancy and reef conservation by avoidance are about the only issues since where and how fast you are going is already determined for you. Two to four miles of submerged distance can be covered depending on depth and temperature. This is the popular form of open water boat diving in many places including Cozumel and the north coast of Central America.