First time seeing one of these in the wild! Dude had a hydrofoil at the bottom of a really long fin. The idea is that once the board hits a critical speed, the foil lifts the whole operation up. It’s probably a good thing in Florida, too, what with the terminally choppy East Coast windswell. Today he looked a little ridiculous. But I have to admit it was neat watching him turn around and ride back out to sea just by pumping to keep his speed up.
Having trouble visualizing? Dig.