Quoting myself to add that this sea cucumber is probably at least part Poison-type, since according to the documentary, the guts expelled by real-life sea cucumbers are toxic.So the description says the sea cucumber Pokemon spills its guts and turns them into a fist to attack. Here's footage of a real-life sea cucumber expelling its intestines.
Oh, and here's a narrated documentary on how they fight using their guts.
Nature is weird!
What amazing creatures! Great concept for a Pokemon.