Navy Special Operators are recognized as some of the world's most feared warriors. Run using the same aquatic training program that tests the mettle of real-life divers and explosives techs, Hellbender's Amphibious Bootcamp sends exercisers plunging in and out of the water as they blast through a blend of calisthenics and aquatic exercises. A diverse collection of former sailors, soldiers, and firefighters lead the classes, shouting encouragement as as students switch from pushups and pull-ups to freestyle, breaststroke, and sprint swims. Movable obstacles including sandbags, weights, and decommissioned bathyspheres also wait beneath the depths, challenging endurance as they bulk up screaming muscles. Classes welcome all fitness levels, but exercisers should be able to tread water, swim at least 25 yards without stopping, and arrive with their own goggles and swimsuit.