The sight of a massive humpback whale thrashing in the sea doesn't usually elicit an invitation to splash around with him.

Humpbacks can weigh in at a whopping 40 tons and stretch 50 feet from nose to tail. That's the kind of heft that easily overturns small boats. And woe to anyone who should jump on the back of one of these behemoths.

But that's just what Sam Synstelien did when he saw a humpback in distress in Central California's Morro Bay this week. The animal was hopelessly tangled in a rope that was attached to a buoy.

Synstelien, along with crewmate Nicholas Taron, had already tried reporting the unfortunate whale to the U.S. Coast Guard — but they were told it would be hours before rescuers could be dispatched.

Hours, the commercial fishermen figured, this whale didn't have.

"If we wanted the whale to survive we had to go get it," Taron later told Inside Edition. "We thought there was no other option for the whale; we decided to go for it. We were so pumped up full of adrenaline, I don't think we were that scared."

Easy for Taron to say, of course. His role in the rescue was mostly in the enthusiastic cheering department.

In the clip, you can hear him quarterbacking the operation from the side of the boat while filming the entire operation.

"Swim! Swim!" he yells. "Move! Just get it! Get it!"

A humpback whale spouts off the coast of Mexico. Humpback whales are famous for their songs. But if the whale spotted in California's Morro Bay was singing anything, it was a very sad song — until the fishermen showed up. (Photo: Steve Adcock/Shutterstock)

"[The whale] was just swimming in counter-clockwise circles," Taron later told KNTV. "You could tell he was stressed and being held to the bottom."

The very agitated whale didn't take well to human intervention and even slammed its massive tail against the boat. But Synstelien hung in there, at last slicing through the rope that bound the creature. And then with an unceremonious whoosh, the great whale dove deep down beneath the roiling waves.

It wasn't much of a thank you, but Synstelien and Taron were left with a whale of a tale.

Fisherman jumps on a thrashing whale's back to save its life
When California fishermen spotted an entangled humpback whale, they didn't hesitate to help.