U.S. Special Forces refine combat diving to improve covert maritime access to defended coastlines.

U.S. Army special operations forces are training at Naval Air Station Key West in Florida to improve maritime infiltration skills through the six-week Combat Diver Qualification Course. Overseen by the 2nd Special Warfare Training Group (Airborne), the course prepares U.S. Special Forces, other special operations personnel, and selected foreign troops to conduct maritime missions where conventional access routes are too exposed or difficult to use.

U.S. Army special operations forces are developing surface and subsurface access capabilities through combat diver training at Naval Air Station Key West. The six-week qualification course, conducted under the 2nd Special Warfare Training Group (Airborne), brings together Special Forces soldiers, personnel from other U.S. special operations components, and selected foreign troops. Training is intended to prepare them for maritime missions requiring alternatives to conventional approaches that may be exposed or difficult to employ.

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A U.S. Army Special Forces Combat Diver Qualification Course student conducts open-circuit scuba training off NAS Key West, Florida, in February 2026. (Picture source: US DoD)

The Special Forces Underwater Operations school in Key West covers a broader range of skills than military diving alone. Students train in surface and subsurface infiltration and exfiltration, beginning in a controlled environment before moving into open water, then combining diving with airborne insertion, helocasting, and small-boat operations. This progression addresses a specific special operations requirement: reaching an objective from an unexpected direction while reducing the physical and visual signature of the unit.

In an article published on October 2, 2026, the U.S. Army detailed how the John F. Kennedy Special Warfare Center and School organizes this training and prepares selected personnel in open-circuit and closed-circuit diving, underwater navigation, and maritime infiltration. The objective is to produce divers able to operate in complex coastal environments while retaining the skills required to transition from maritime insertion to operations ashore.

Candidates arrive after completing demanding preparation. Each Special Forces group conducts its own Maritime Assessment Course and combat diver preparation before issuing the validation required to attend the qualification course. Once in Key West, students complete a U.S. Army fitness test, receive and inspect their equipment, and enter the pool on the second day. The school uses a renovated 62,000-cubic-foot pool, approximately 1,755 cubic meters, to teach emergency procedures and basic techniques before exposing divers to currents, limited visibility, and other conditions encountered at sea.

The first two weeks focus on basic open-circuit diving, including emergency procedures and an individual confidence test designed to determine whether a diver can resolve equipment problems underwater without losing control of the situation. Students then move into advanced training that includes deep dives. They also study diving physics and physiology, marine hazards, tides and currents, all of which become important when an infiltration requires a team to travel a substantial distance underwater rather than simply leave a surface vessel or craft.

A new phase begins during the third week with closed-circuit diving using a Lung Activated Rebreather. Unlike conventional open-circuit equipment, which releases exhaled gas directly into the surrounding water, a closed-circuit rebreather recycles part of the breathing gas. This reduces bubble production and therefore the diver’s visual signature, which can be useful during a discreet approach toward a monitored coastline. The U.S. Army article does not identify the exact Lung Activated Rebreather variant used during the course, so the performance characteristics of a specific model cannot be attributed with certainty to the equipment shown.

Students learn to assemble, maintain and test their rebreathers before leaving the pool for the ocean. Navigation then becomes a two-person task. One diver follows the route using a compass board, while the second monitors obstacles and the immediate surroundings. During the fourth and fifth weeks, these individual skills are integrated into eight-to-12-person elements conducting advanced closed-circuit dives and beach landing site infiltrations by day and night. The increase in scale is operationally relevant because an infiltration must deliver the full detachment to shore while maintaining cohesion and preserving enough physical capacity to continue the mission on land.

The tactical value of the course lies in combining several insertion methods rather than treating combat diving as an isolated skill. Students train in surface infiltration using Combat Rubber Raiding Craft, conduct parachute jumps into the Sgt. Maj. Jerry D. Patton Water Drop Zone and perform helocast insertions from helicopters before continuing their movement on or below the water. The course ends with a three-day tactical exercise combining a combat dive infiltration, movement toward a guerrilla base and a subsequent dive linked to a raid. In practical terms, qualified personnel can shift between airborne, surface and subsurface approaches depending on coastal defenses, geography and the level of surveillance around the objective.

This flexibility is increasingly relevant as maritime approaches are monitored by coastal radars, uncrewed systems and persistent sensor networks. Subsurface infiltration does not eliminate those threats, but it gives U.S. special operations forces another option for approaching islands, ports or defended coastlines without relying exclusively on aircraft or conventional landing craft. Training selected foreign personnel at Key West also supports the use of common procedures with U.S. forces. As military competition places greater emphasis on littoral zones and strategic waterways, the ability to move from air to sea and then below the surface remains a distinct access option that cannot be fully replaced by stand-off weapons or uncrewed systems.

Written By Erwan Halna du Fretay - Defense Analyst, Army Recognition Group
Erwan Halna du Fretay holds a Master’s degree in International Relations and has experience studying conflicts and global arms transfers. His research interests include security and strategic studies, particularly the dynamics of the defense industry, the evolution of military technologies, and the strategic transformation of armed forces.