It's been said there's safety in numbers, and long-distance swimmer Adam Walker is a true believer.
Walker, 34, was halfway through his swim across the Cook Strait in New Zealand last Tuesday when he spotted a shark coming directly at him.
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"A fin kind of flew towards me...and then went underneath me," Walker said from his home in Nottingham, England during an interview with KITV4.
Walker believes the shark was a 6-foot great white, a species common to New Zealand waters.
"All I know is it had big teeth and it looked like it would bite," Walker said with a chuckle.
As the shark parked itself directly beneath him, Walker felt as though his nerves might get the better of him and he would have to stop. But within mere seconds, a pod of dolphins surrounded Walker as if providing protection.
"I felt very, very secure because of the dolphins," said Walker. "I felt like they were my mates and I was part of the pod."
Walker posted a video of his experience on YouTube, and so far it's received more than 3.8 million hits. His girlfriend also snapped photos of the encounter as she sat on a nearby skiff, and one picture in particular has gone viral. It shows Walker coming up for a breath of air as a dolphin leaps out of the water near his guide boat. The picture is positioned so perfectly that some are questioning its authenticity.
"Yeah, they just think it looks too good and I'll take that as a compliment because it was a cheap camera," he said.
Walker estimates there were about 10 dolphins in the pod, and they swam with him for over an hour until the shark lost interest and veered off.
"Maybe they thought I was a wounded mammal or something and they came to support me," he said.
According to David Schofield, a marine mammal health and response program manager at the National Oceanic and Atmospheric Administration in Honolulu, dolphins will often track other animals as part of their normal behavior. However, Schofield didn't discount the notion that dolphins may have been protecting Walker from the shark below.
"We do get reports of dolphins coming up to people and they appear to be giving aid," he said.
Walker was swimming across the Cook Strait in his attempt to become the first Brit to complete the Ocean's Seven, a series of long-distance swims across seven of the most grueling channels the world has to offer. To date, only one other person has completed the challenge on the first try, and Walker has already finished six of the seven crossings.
Ironically, Walker is raising funds for whale and dolphin conservation as he hops around the globe.
"It's almost like they were tuning in to what I was doing," Walker said of his encounter with dolphins. "I always knew they were intelligent, but it totally backed up my view of these incredible mammals."
Walker completed the Cook Strait in eight hours and 36 minutes. In June 2012 he swam the Kaiwi Channel from Molokai to Oahu in just over 17 hours despite being stung repeatedly by Portuguese man-of-war.
Walker hopes to return to Oahu next year to do some motivational speaking and conduct a swimming clinic for kids.
He's scheduled to complete the Ocean's Seven in August when he attempts to cross the North Channel between northeastern Ireland and southwestern Scotland.
To follow Walker on Facebook and Twitter or donate to his cause, click on the "As Seen on Section" of KITV.com