Wikipedia
Helocasting is an airborne technique used by small unit, special operations forces to insert into a military area of operations. The small unit is flown, by helicopter, to a maritime insertion point. Once there, the aircraft assumes an altitude just above the water's surface and an airspeed of or less. Team members then exit the aircraft and enter the water.
In some cases, depending upon the mission parameters and the aircraft used, personnel may be inserted along with an inflatable boat for over-the-horizon operations. When a fully inflated boat is transported and inserted with personnel, this type of operation is known as a "hard duck". In cases where a fully inflated boat cannot be accommodated by the aircraft, it can be partially deflated for transit and inflated at the insertion point by means of a foot pump. This type of operation is known as a "soft duck". If inflation to any degree is not feasible, a "rolled duck" may be performed.
Once team members are in the water, they may swim to the objective or, in the case of a "hard duck", "soft duck", or "rolled duck", conduct an over-the-horizon transit to the objective, via inflatable boat.