1 Dirque: Whale off the port bow!
2 Long Tom: Hard a starboard! We be havin' no truck with whales.
2 Wendy: Aye, cap'n!
3 Dirque: Wait! It not be a whale! It be some sort o' underwater boat! With men bein' comin' out o' hatches!
4 Long Tom: Aha! An underwater boat o' the year 1940! She'll be no match for our cannon! Be preparin' to board!

Pirates generally didn't, but many other people used to hunt whales. (A few still do, but let's not go there today.)

The most commonly hunted whale species by European whalers was the right whale. The name, interestingly, comes from the simple fact that these were considered the "right" whales to hunt, because of the usefulness of their carcasses and the fact that they floated when killed.

This is the sort of etymological story that sounds so cute and quirky that it's usually completely false and only propagated because it is so quirky. But in this case it happens to be true.