Vincent doesn't exactly feel comforted, but the simple instruction gets him going again either way. Now that he's substantially in the water, he's momentarily more concerned with being left alone than he is with anything in the depths trying to eat him.

So he follows. And at this point there's enough water resistance to fight through that he starts doing sort of a half-swimming, half-walking thing just to keep from falling too far behind.

"There are nice things in the water too, you know," Robin says conversationally, again doing a very lazy backstroke in a manner that would be infuriating to Vincent if he could see, "Beautiful fish. Some ducks. They mostly don't bite."

"What are... Ducks?" Vincent asks, feeling like he's being pranked.

"...What?" Robin looks astonished, "Have I seriously never told you about ducks before?"

Well he's about to tell him about ducks now.