The only two branches that require swimming (not just water safety/survival) as a mandatory skill prior to enlistment, during basic training, and throughout one’s military career are the U.S. Navy and U.S. Coast Guard. All other branches of the U.S. military, at a minimum, may include water safety/survival skills during their basic training, as part of training for other specialized jobs within their branch, and/or throughout one’s military career (depending on their specific job), but it is not mandatory for enlistment unless you are enlisting into a specialty job and/or at a higher rank within that particular branch which requires such skills.