These are swamp buggies. With horsepower figures in the four digits, they can drive on land, but they race in the water. What they do looks as much like riding an exploding bomb as any kind of motorsports I've seen.
You can read up a history of these buggies that are now just too fast for hunting and only good for racing right here on SwampBuggy.com.
Here's what the races look like on the outside, down at the 2013 Swamp Buggy Races in Naples, Florida. Where else but Florida?