I have always felt like the water survival training is super-safe. It sounds like maybe some type of medical complication.
http://abcnews.go.com/US/wireStory/major-dies-fla-air-force-survival-training-17500865#.UH9ZxWfwr4A
http://abcnews.go.com/US/wireStory/major-dies-fla-air-force-survival-training-17500865#.UH9ZxWfwr4A