Cypress Rojas, 5, got an up-close look as the massive creature repeatedly surfaced in front of them.
"It was coming to us and then it flicked its tail, and then it went this way and we saw another one," the girl said.
At 59 to 89 feet long, fin whales are the second largest whales on Earth.
Wildlife photographer Mark Girardeau also captured a birds' eye view of the encounter. From that angle, you can appreciate the sheer size of the whale in comparison to the boat.
Experts say an unusually high number of fin whales are off the Southern California coast right now, possibly being drawn here to feed in warmer waters.