A Spinosaurus could grow up to 15 metres in length. What is that in centimetres? What is it in millimetres?

Challenge: A large T. rex was only 80% the length of a Spinosaurus. What is the size of the T. rex in centimetres?

Fact: The Spinosaurus is the only known swimming dinosaur.

Question: What other creatures lived in the sea at this time? Do any still exist?