Plenty of strong, fit recruits get caught out by the Navy swim assessment, and almost always for the same reason: they trained for the wrong thing. Three of the four elements are survival skills, and the biggest by time is fifteen minutes of doing as little as possible.
Train hard freestyle for eight weeks and you arrive fitter and no better prepared. The recruits who get through are the calm ones, because the thing being measured is composure in the water. That is a skill, and it can be built.

