It sounds like a fishy tale but if one man's dog did not take on a shark, he may have lost his leg - or his life.

The drama unfolded when fisherman James White landed a 180cm shark which managed to bite down on his ankle as it thrashed around on the ground.

Watch the video above: Snake regurgitates dog after swallowing it.

It would not let go and its teeth quickly sank deep into his flesh. White was worried.

But then his one-year-old, 45kg pitbull Darby leapt into action.

“The first time I told somebody this, they were like, ‘You’re out of your mind, there’s no way that happened’,” the Californian man said.

“Then I showed him the pictures and I’m like, ‘No it absolutely happened’.”

White was fishing from the shore at Bodega Bay in Sonoma County California last month when he felt a pull on his line and spent the next 10 minutes trying to reel it in.

He finally landed the aquatic beast - a 180cm long sevengill shark.

Saving his master was all in a day's work for Darby. Credit: NBC

White went to remove the hook from the shark when it twisted, fell to the ground, and sank its teeth into White’s ankle.

“Immediately there was blood everywhere, the first bite punctured an artery,” he said.

“The pressure was intense."

He has left Darby in the car a short walk away, but White's loyal canine heard his human friend yell and struggle and leapt through the car window, raced down the hill to the shore and tore into the shark.

He into the shark’s gills, causing the shark to sink its teeth even deeper into White.

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“And I told him, ‘No back off’ and then [Darby] repositioned and grabbed it by the tail,” White said.

“He literally ran up the hill with it and pulled it off my leg.”

White tossed the shark back into the water and it swam away.

He says Darby saved his leg from more damage, possibly severing the artery it had already punctured.

"He’s been a part of the family from day one. Just now a little more. If it wasn’t for him I would have been a lot worse,” said.