Some water dinosaurs still alive? What do you think?

Think about it. Some water dinosaurs may still exist. Because dinosaurs of water, lived thousands of feet under water, and the comet, which made the extinction, I don’t believe it could reach such a depth to kill dinosaurs. Anyway these are just thoughts. But what about the lochness monster?? We have so little evidence but plenty of believers!! But hey the animals we have are dinosaurs.. There grandparents where giant creatures. So if all the dinosaurs died why do we still have animals??? Think about it. It might be stupid but dinosaurs worth some thinking