When siblings Kaydn and Reef Persidok took to the waves at a popular surf spot off San Diego County recently, they had no idea they weren't the only ones catching air. Footage of Reef riding a wave shows a juvenile great white shark in the background launching itself out of the water in typically dramatic fashion.

"Anybody else feel a little sharky vibe yesterday out in the lineup?" Kaydn Persidok wrote on Instagram. The clip was filmed at Seaside Reef in Encinitas along North America's southwestern coastline where white sharks are known to hang out. "A little while before we saw the shark breach, my friend said she saw something that looked like a shark swim right under her, and right then it got suspicious," Persidok told The CW San Diego. "Then as we saw it breach my heart raced and I was amazed and stunned but also a bit scared because it wasn’t too far away from us!"

Acoording to Dr Chris Lowe, who heads up the Shark Lab at California State University in Long Beach, a number of white shark nursery aggregation sites have been identified around San Diego beaches, so juveniles are sporadically seen in the area. Although breaching behaviour in sharks is not fully understood, there are a number of theories. "Many of these young sharks are covered with parasitic copepods that move along the skin – this could cause irritation ... so the sharks may breach to try to dislodge these itchy parasites." Dr Lowe explains. Another explanation could be that the sharks launch themselves out of the water when chasing schooling fish like anchovy, sardine or topsmelt, however, breaching has been recorded even in the absence of these prey species. It's also possible that great whites simply "jump because they can," Dr Lowe adds.

Despite the close proximity of the breaching shark, the surfing siblings did not have any further encounters with the predator. "I respect the ocean and all the wildlife and creatures in it," Kaydn said. "I think it’s really cool to see a shark breach while a surfer is riding a wave! I’ve never seen that before."

Top header image: David Remsen/Flickr