NZ spearfisherman fights off sharks in dramatic video

Dramatic footage has emerged of a New Zealand man's close call with two Galapagos sharks.

Nat Davey stabbed the sharks in the head after they attacked him on a diving trip at remote Ascension Island between Brazil and Africa.

Mr Davey had speared a huge yellowfin tuna when two sharks started swimming at him.

The first shot up above the surface, and whipped him with its tail fin.

The 39-year-old tried to haul the tuna up again, but the sharks came back for more.

This time Mr Davey decided to fight back. He stabbed the first shark in the head, and when the second swam up for another go he did the same again.

Mr Davey admits his memory of the attack is pretty foggy, but says his instincts took over. He says it wasn't until he saw the video that he realised how much of a close call he really had.

The experienced spearfisherman estimates the sharks weighed between 150 and 200 kilograms each.

He says they're similar to bronze whalers - a species known for unprovoked attacks on humans.

You'd think that was enough adventure for one day, but he says he only took a five-minute break before jumping straight back in the water.