Scubacraft
Underwater shenanigans await aboard the Scubacraft ($120,000). This open-cockpit submersible can reach 50 knots above water thanks to a 250hp engine, and offers push-button descent down to 100 feet beneath the waves, where electric thrusters kick in to move you and up to two friends around the depths. Scuba gear and certification required for the captain and passengers, but if you're seriously considering buying this thing, that's probably not going to be a problem.