The motion didn't pass him; he waved back, then managed to kick himself down a little lower, turning over in the water and grabbing a plant to keep himself down there, practically back to the ocean floor, looking up. It was... very quiet. He could hear the hum of boat motors distantly, the cavitation of props, but mostly it was quiet.

Still, he wasn't a fish and couldn't hold his breath forever, though he probably would have been perfectly content to lay on the bottom and look up at the bands of sun for quite a long time. He let go of the plant and floated back up to the surface, sucking in a breath of air with his head tipped back a bit, then grinning just in general. At nothing in particular.