Sinclair is forced back onto the seat as the bathysphere takes a sharp curve, and he ends up on the floor, hanging onto the seats for whatever kind of security they can offer.

This was definitely not part of the plan. Even if it should have been, it wasn't. Sinclair tries to rifle though everything he's learned about Ryan's defense system for some sort of piece of instruction he can offer Jack, but he comes up dry. A missile was fired, the only thing to do is try and avoid it. And that part's already in action.

"Get us straight again, kid!" he shouts, "Straighten us out!"