Fame
Not a ton. But hey, the locals may take to calling you the Big Kahuna. So there's that.
Sadly, the world at large will never hear of the lives you've saved, unless you fish Brad Pitt from the surf. If that's the case, then you'll be the talk of the town for, well, maybe a day or two. He might even name one of his kids after you. Hey, you've got to like your odds there.
If you save a kid from drowning at the swimming pool, or successfully administer CPR at the waterpark, you'll probably get a shout out in the local paper or on the local news. Just be sure to tell your parents to set their DVRs and buy extra copies—it'll likely be a one-time thing. Save a copy for yourself, too. It'll come in handy when your future kids are complaining about having to get up early to take swim lessons.