Rescue teams raced to the scene within minutes of getting calls for help, but it was too late to save two of three divers who ventured into the depths on Snake Wall, in the waters of Georgia Strait.
The rock wall, described on some diving websites as "the abyss," plunges to more than 180 metres on the north side of Snake Island, just a 15-minute boat ride from Nanaimo.
The three divers, Washington State residents whose names have yet to be released, left the charter boat Sea Dragon on Friday afternoon and began a dive that was to take two of them to extreme depths. One diver, who survived, held at a shallower level before returning to the surface.
"There were three people that buddied up for this deep dive," Donnie Reid of the Dive Industry Association of BC said in a statement Sunday. "Complications arose on the dive. One of the divers made it safely back to the surface and is in good health. The two other divers in the group were not as fortunate."
Mr. Reid said he didn't want to speculate on what might have gone wrong and would await findings from a formal investigation.
"There's very little detail right now," Mr. Reid said. "The police have passed it on to the coroner's office … Because it was underwater and there was only the three of them, there is only speculation now on our part as to what happened."
He did say one of the two divers who died had managed to struggle back to the surface, but rescue workers were unable to save him.
"One diver did return to the surface, but later died due to injuries sustained on the dive," he said.
The other diver's body was not recovered until Sunday, by a commercial diver who went to 80 metres.
"They knew just about exactly where he should have been, and that's where they found him," said Barbara McLintock of the B.C. Coroners Service. She said the diver who survived was not in visual contact at the time of the accident, and hasn't been able to say what happened.
"They were highly, highly experienced divers," she said.
Mr. Reid said Snake Island is one of the most popular places to dive on the West Coast, which is regarded as one of the best locations in the world for recreational diving because of its cold, clear water where sea life abounds.
The small, rocky island is located just outside Nanaimo's harbour, on the east coast of Vancouver Island. It lies on the busy Horseshoe Bay-to-Nanaimo ferry route and is a diving hotspot because of its rich marine life and two nearby wrecks – the HMCS Saskatchewan and the HMCS Cape Breton, which were scuttled near the island to create artificial reefs. The two navy destroyers lie in about 40 m of water, within easy reach of most recreational divers.
Snake Wall, however, is a more challenging feature that plunges down the north side of the island. Mr. Reid said the three divers reportedly headed deep down that wall, with two of them reportedly expected to go to about the 70-m level.
"My understanding is they were fairly experienced divers," he said when asked if the divers had headed for unsafe depths. "Recreational diving today has moved into a different realm. We have technical divers who have had a lot of training, but like anything, people are pushing back barriers. That's just a general comment, not specific to this accident."
He said he would not call technical, deep diving dangerous.
"Diving is a safe sport – but it's an unforgiving environment," he said. "I'm trying to think if there's any other activity out there where you are so dependent on supplying your own life support. The only thing that really comes to mind is going to space."
The accident has sparked discussions on dive websites, where users are wondering what happened.
"Seems like a pretty deep profile, regardless of the location," a dive master identified as ibj40 posted on Scubaboard.com. "The question is whether they were prepared to make this dive, and what went wrong."
"Snake Island wall is commonly used as a training area for tech diving due to the fast drop off and easy navigation (all upward slopes lead to the Island)," wedivebc said in another posting. "I don't know anything about the divers involved but I do know enough about the dive charter operator to know they would be very unlikely to knowingly let someone do that type of dive off their boat without proper training and equipment."