The search for an award-winning Canadian film maker, who campaigned to protect sharks, continues off the coast of Florida after he went missing two days ago.
The parents of award-winning Canadian filmmaker Rob Stewart, an environmental activist campaigning to protect sharks, said on Thursday they hoped his experience in the water can help him survive.
Mr Stewart, 37 disappeared on Tuesday after a deep water dive to retrieve an anchor.
"If anybody can survive in the water, it is him," the filmmakers father Brian Stewart said.
"A bunch of the people in the boat gave their attention to the guy who collapsed and a minute later they turned, and Rob was gone. They haven't seen him since," he said.
At the time of the incident, Rob Stewart was filming a new documentary called Sharkwater: Extinction, which he was aiming to show at the Toronto International Film Festival later this year, his parents said.
The US Navy, US Customs and Border Protection, Florida wildlife officials, a county sheriff's office and civilian volunteers have joined the Coast Guard in the search for Stewart that is using ships, helicopters, aeroplanes and dive teams, the Coast Guard said.
"We would not still be searching for him if we could not find him alive," said Petty Officer Eric Woodall, a Coast Guard spokesman.
His mother, Sandy Stewart, said support was pouring in from all over the world.
Rob Stewart's 2006 documentary Sharkwater was aimed at exposing the shark hunting industry that was feeding demand for fins, a delicacy in Chinese cuisine.
With finning, typically the fins are cut off and the live shark is tossed back into the sea. Unable to swim properly, the shark suffocates or is killed by predators.
Stewart said his new film was looking at other ways that as many as 80 million sharks are being harvested each year for items ranging from cosmetics to pet food.
"Sharks are sophisticated, intelligent and often shy creatures that aren't interested in eating humans," he said in a video seeking funding for his new movie.