People really underestimate these guys. They may be the best black pearl harvesters in the game. They collect tons of them from the giant shells and get a crazy weight reduction on them. Not that they even really need it, since their weight stat is astronomical. When you're riding these guys you can close their shell to make your player invincible. They also provide infinite oxygen under the water and insulate you against heat and cold. From what I can tell they don't dismount you when shocked. When free swimming their tail attack has solid DPS and they take reduced damage to most of their body. On land their tail attack does impressive knockback. They also have a really solid health pool that pairs well with their natural armor. With one of these guys you can basically live inside the ocean for as long as you want. The only real downside is their speed, but if you breed a couple of high level individuals and max out your imprint you may be able to get a 200% speed baby like I did. Helps a lot.