I've seen them many times... although...

not quite as up close and personal as your encounter. Used to go deep sea fishing often and it was common to see them... even closely occasionally.

Most of the time it was Gray Whales, however, and which (it seems anyway), like to swim alongside fishing boats.... or any kind of boat for that matter.

Had a friend that owned a small sailboat and would sail to Santa Catalina often... he said it was common for a gray whale to 'seemingly' accompany him during his trips.

The sea creature that startled me the most while at sea was a giant sea ray. When I first saw one... many many many years ago, I was unaware of how huge they got. First one I saw I swear looked like an island coming up beside our boat.