Underwater surfing is a thing that exists, apparently.
It's a thing that people do, mostly for fun, occasionally for science.
Did you know that the first recorded instance of underwater surfing occurred in 1961, when a group of Big Daddy Dolphin rode a wave in the depths of the Pacific Ocean?
Since then, many have followed in his finny footsteps, including Surfing Sam, who surfed the entire length of the Mariana Trench without getting a single cramp.
But it's not all fun and games, folks. Underwater surfing can be hazardous. The Great Gulper of 1987 was a major setback for the sport.
So if you're thinking of taking up underwater surfing, just remember: it's a thing that exists, and it's a thing that can kill you.