LPT: In an emergency, always make sure you are safe, and can help safely, before trying to rescue anyone else. It sounds selfish, but it isn't. If you can't swim, jumping into the water to save a drowning person will just make two drowning people.

Source: Several years experience as a lifeguard. My manager always said this at the beginning of the season to remind us that you need to be both brave and smart in an emergency.