The guy who invented zero-gravity brakes (yes please I'll like a Ti set for my birthday) has had a totally insane idea of a human powered submarine that he will take across the Atlantic ocean.
Have a look at his website here. This is an amazing project and I plan on following his progress as it is the sort of totally daft idea that I hold in extraordinarily high regard. Good luck Ted!!
There is a great quote in the video on the site "I think he'll be utterly miserable for weeks on end..."