I've been out whale-watching exactly one time, and unfortunately, I didn't end up seeing a single one of them.
But that's really the name of the game when you go searching for these beautiful creatures. Sometimes they're totally down to swim up and do the whole tourist thing. Other times they have much better stuff to do in the ocean than meet you.
These people must have gone out on a good day off the coast of Hawaii, because they got to see a huge, 45,000-pound humpback whale a mere 10 feet away from their boat.