Some magnificent bastards designed and built an extreme prototype of a personal watercraft that can travel above and below the surf. The Bionic Dolphin was homebuilt by Tom Doc Rowe and Dennis Dusty Kaiser of Redding, CA, using an engineering methodology they developed, called "Hmm..that looks about right." The Dolphin is powered by a modified 100 HP Evinrude inboard, and a turbine compressor that charges the craft with air for underwater runs. Cooler than hell, we say, for something without wheels.
Doc and Dusty s Totally Outrageous Submersible Flying Machine [The Bionic Dolphin]