The British long-distance swimmer was in the midst of a 16-mile journey across New Zealand's Cook Strait when he noticed a great white shark trailing beneath him. That's when a group of 10 dolphins swept in and accompanied Walker until the shark swam off, about an hour later.
The pod might have been executing a rescue attempt or just having some fun with a fellow swimmer. Deliberate or not, this isn't the first time dolphins have protected a human from danger in the water, preventing shark attacks and drownings or aiding broken-down boats.
Upon safely completing the swim in less than nine hours, Walker posted enthusiastically on Facebook, "I'd like to think they were protecting me and guiding me home!!!"
At the very least, the dolphins helped Walker finish the second to last of the Ocean's Seven—a series of the world's hardest long-distance ocean swims that only one other British person has ever completed. His last challenge, the North Channel separating Ireland and Scotland, hopefully will remain shark-free.