This creature just saw a massive slug in the water around the size of a rabbit just removed its own head, and now the head is trying to get away from the body. This is a normal thing that this slugs does to survive in the wild, the head of the slug will detach itself to get away from its own body if it’s sense it has 1 or more parasites in its body. The head will go on the grow a new body. (This is based off a actually thing like 2 sea slugs can do)