British swimmer Adam Walker recently set out to raise money for the Whale and Dolphin Conservation Society by swimming Cook Strait in 8 hours 36 minutes.

Cook Strait is between the North and South Islands of New Zealand. It connects the Tasman Sea on the northwest with the South Pacific Ocean on the southeast.

When Walker started his swim he noticed a large shark, possibly a Great White beneath him. Just as the worry had begun to set in, a pod of dolphins appeared from nowhere and the shark took off.

For over an hour the dolphins stayed with Walker as he took on the Cook Straits from Wellington to Perano Head, a nearly 16 mile swim.

This video, taken from the guide boat, shows the dolphins gathering around Walker and protecting him as he swims. Coming so close he was even touching their tails as his hands dipped in the water.