I am under the impression that the people that do the open water rescues are Coast Guard Rescue Swimmers.

2.12.3 DOD resources that may be available to assist include Air Force pararescue personnel, and specialized teams such as Army, Navy, and Air Force explosive ordnance disposal (EOD) teams, Navy sea-air-land (SEAL) teams, or CAP ranger teams.

2.13.3 Air Force: resources include limited numbers of helicopters and fixed-wing aircraft capable of being used for civil SAR purposes. In addition, limited numbers of pararescue personnel may be available to assist civil resources in specific situations.
… f) Pararescue personnel, SAR personnel highly trained in such fields as parachuting, mountaineering, survival in all environments, advanced emergency medical care, underwater scuba swimming, and aircraft crash fire fighting, can deploy from aircraft over any type of terrain or ocean, day or night, to assist survivors. The pararescue team usually consists of two pararescue personnel equipped with emergency medical care kits, survival kits, and either scuba or forest penetration parachute kits.

5.2 Terrain
5.2.1 The terrain may determine the type of search pattern needed and the SAR facility selected. Highly maneuverable aircraft effective at high altitudes may be required in rugged mountain areas. Helicopters may not be able to operate in the thin air and turbulence associated with mountain contour searches. The survival kit carried by the distressed craft and the hoist devices available also influence decision-making. Dense foliage may hamper visual and electronic searches and require a greater number of aircraft and ground SAR facilities, and closer search track spacing. The presence of electrical power lines, towers, and bridges should be considered when planning search altitudes and areas. Prominent landmarks can be used as boundaries and checkpoints for laying out aeronautical and ground search areas. Some aircraft may have poor navigation equipment, and some members of ground parties may be inexperienced outdoors and more effective when using readily recognizable boundaries. The type of rescue team used after the distress site has been located is also terrain dependent. Local law enforcement authorities, forest service personnel, mountain rescue clubs, ski clubs, or pararescue personnel may be required.

6.10 Rescues in Difficult Environments
6.10.1 Certain geographical areas with unique terrain, weather, or accessibility conditions pose special considerations.

6.10.2 Pararescue teams can place medically trained personnel at the distress scene with a minimum of delay. These teams are qualified for jumping into both open ocean and land environments. RCCs are to maintain a list of available pararescue teams, their basic capabilities, and means for requesting their use.

Polar Environment.

6.10.4 Immediately upon …
a) Polar survival professionals may assist. Pararescue teams should be considered as a primary means of polar rescue. Appropriate agencies should be alerted and briefed as to the possible need for pararescue teams.

6.20 EMS Personnel
6.20.1 Emergency medical services personnel are trained to provide emergency medical care lifesaving services at the distress scene. In addition, these personnel may be trained to provide life support and life-sustaining services during survivor extraction from wreckage, evacuation, and transport to a receiving medical facility. They include SAR crewmen and pararescue personnel qualified to administer basic lifesaving first aid and trained EMS personnel such as doctors, nurses, corpsmen, paramedics, or SAR emergency medical technicians (EMTs).