Specialists are not any clearer on why three tropical sea turtles have been found stranded on Vancouver Island, but say the chances of survival for the most recent arrival do not look good.

The sub-adult male was found Wednesday, after an olive ridley and another green sea turtle have died in the past two weeks from exposure to B.C.'s hypothermic waters. All three were taken into care at the Vancouver Aquarium.

Veterinarians now are working to revive the turtle but cannot find a heart beat. Dr. Dennis Thoney said a heartbeat can be hard to find in cold-stunned cases but there is hope for the animal yet.

"It's been laid out, it doesn't have a heartbeat, but we're still checking to make sure it's alive as we warm him back up," he said.

A Pacific Rim National Park visitor was walking the popular Combers Beach in Tofino when they saw the turtle stranded on the shore and called park staff.

The Department of Fisheries and Oceans arrived to assess the turtle's poor condition and carried it on a stretcher off the beach until he could be transported to the Vancouver Aquarium.

Thoney said it is unusual that green sea turtles keep washing up in B.C. but it could be in part due to a warmer fall that led to the animals being caught off-guard by a sudden temperature drop.

"Their bodies start to shut down into a cold-stunned state which would have left them drifting at sea before eventually washing ashore," said Thoney.

"All of what we are saying is speculation," he added. "We know that they're too cold and they haven't been able to function or swim. But how and why they got here is a difficult answer."

Thoney said the recent sea turtle discoveries have been bittersweet. Their rare occurrence has allowed the Aquarium to learn about what threats these red-list endangered species face but their deaths have been regrettable.

According to Vancouver Aquarium's B.C. Cetacean Sighting Network, this will be the sixth sea turtle sighting of 2011.

Any sightings of live, free swimming sea turtle and cetaceans should be reported to the Vancouver Aquarium's B.C. Cetacean Sightings Network at 1-866-ISAWONE.