Dive (three books) by Gordan Korman

If you are not into reading long books, this is the series for you! Each book is only a little more than a hundred pages. The characters felt like real teenagers and the action was non-stop. You also learn lots of nifty stuff about scuba diving, sharks, old pirate ships, scurvy and color blindness. He also has a series called Everest that I recommend as well.