The Grasp - A Kraken-Like Mob

The grasp would be a hostile mob resembling a kraken, found rarely in deep ocean biomes.

It would have eight tentacles, four for grabbing and four for attacking. It would try to grab nearby players and dolphins. It would try to hold them underwater long enough to drown them, but it wouldn't attack a player or mob unless it was hit first. The only way to escape the grasp would be to deal enough damage to it in a short window of time. However, since it attacks you whenever you hit it, you would need to keep an eye on your health, too.

The grasp would have 50 health and drop xp and a new item: the grasp tentacle. It would make your melee attacks have longer reach (basically a crab's claw, but for weapons).