Wash matches his pace to jellyfriend's as best he can and points forwards with a tentacle. It shouldn't be far.

He's looking for a cave with a platform; once he finds one, he's going to gesture to jellyfriend - wait, stay here - and clamber up onto the rock and out of the water, and turning back into a human in the process. He sits up and waves at jellyfriend. Hey, buddy.

After all, jellyfriend wanted to know what he really was, right?