I've done a few shark dives and have been nibbled at by a six or so foot barracuda within the Bermudan atoll. On top of my thesis I will be assisting my adviser with a grant he received from the state of New York regarding their artificial reef settlements. Basically I will be doing SCUBA surveys alongside acoustic data swathes to determine whether or not they are actually helping rebound struggling fisheries and endangered species. And I swam competitively, not SCUBA. :P You can free-dive competitively though. Come to think of it, you can spearfish while SCUBA diving which has its own competitive clubs (similar to fishing and free-dive spear/slingfishing). A lot of areas ban SCUBA spear-fishing though since it's very easy to wipe out an entire fishing ground within a single season.