The Scubaboat is a zippy little powerboat that can scoot across the water at speeds of up to 50MPH. But that's just its basic function. If you really want to show off with it, just point its nose down towards the water; it can dive down up to 100 feet.
Yeah, you'll need to have something hooked up to allow you to breathe underwater, as it's an open cockpit, but I'd like to see any other boat do that. I'm not quite sure what the benefit of that ability is, but it sure is cool. And it can be yours for a mere $164,000.