3. Mammoth, Holiday World & Splashin’ Safari, U.S.A
Roller coasters and water slides are notoriously stomach-churning, and that’s while you’re safely strapped or enclosed in a raft or tunnel where all you have to do is enjoy the ride and not think of the churro you just had, but the Mammoth waterslide forces you to focus with its 6-passenger “round spinner” boats. You have two handles to hold onto for dear life across 1,763 feet of aggressive twists and drops, with the largest drop being 32 feet.