Thinking about how ducks and geese look and sound almost exactly the same as they did over 65 million years ago:
(Art above by artist Nicole Fuller)
This is Vegavis, the oldest known bird of the class Anseriformes. If it looks familiar, that's because it is literally a duck. Vegavis was closely related to modern ducks and geese, with preservation of the sirynx implying it quacked like a duck. Vegavus lived in antarctica around 68-66 million years ago placing it firmly in the late cretaceous period. The diving waterfowl we throw bread at have been doing duck things almost unchanged since before the rest of the dinosaurs went extinct.
Since common knowledge is that birds are derived dinosaurs, the best way to get the true cretaceous dinosaur experience is not to watch Jurassic Park but rather to piss off a goose.
The ultimate lifeform underwater might be a crab, but the king of the air is a duck and you should be scared.