Jaws- Ahead of Speedboat

A hundred yards behind her an enormous, lazy
fin was beckoning. She did not see it, and while he
stood frozen in horror, he saw it move, in a
leisurely manner, up their trail.
...
He stood erect, searching their wake for the fin.
The thing must have dived, that was it, he had
fooled it. Now, all he had to do was head for the
beach: no fish like that would go into shallow water.
...
He headed dead for the house on the beach.
Two miles away, maybe less. Not all that far.
Suddenly he froze. Halfway between him and the
beach was the fin. He couldn’t understand it. He was
making 20 knots easily: could the damn thing make
30? Could it compute a pursuit curve? “Holy shit,”
he moaned. He curved back out to sea. The fin dis-
appeared.

- Jaws 2, Chapter 2