I know for a fact that you need to know how to swim to pass basic training as a navy seal as well as basic training to become a lifeguard. A marine biologist may also need to know how to swim to be able to get close up to the marine animals that dwell in the waters. A water technician however dose not really require the skill to swim because he can launch or lower equipment to test the water without ever having to step foot in the body of water .
