THE tourist boat that sank near Vancouver — leading to the deaths of up to six people — was capsized by a breaching whale, according to a new claim.

Five Britons were killed while 21 others were rescued in the accident last Monday.

The search for missing Sydney man Raveshan Pillay is continuing but as each day passes his grief-stricken family fear he will not be found.

Previous reports suggested the MV Leviathian II was struck by a rogue wave and capsized or struck rocks near Vancouver Island but the Maritime News now claims a surfacing whale is to blame for the tragedy.

“The preliminary investigation from the local authorities showed that the group of tourists on board gathered on the port side of the vessel seeing a whale coming to them. At same time the whale was passing under the ship, but emerged and hit the starboard side of the boat ... which caused capsizing and sinking,” the site stated.

The UK Mirror quoted Marc Andre Poisson, the Director of Marine Investigations for Canada’s Transportation Safety Board, who confirmed that “most passengers were on the top deck on the port side”, which would have affected the boat’s stability.

But he appeared to give more credence to the claim that a rogue wave caused the vessel to capsize.

“We also know that the sea conditions were such that a wave approached from the starboard quarter, that’s the right of the vessel,” he said.

Whales surfacing under boats is rare but not unheard-of.

In 2014 two Argentinian men in kayaks captured incredible footage of the moment a southern right whale dipped under their vessel and lifted it out of the water.

Both men were unhurt in the incredible incident.

Viral Video: Whale Lifts Kayakers Onto Its Back Two kayakers in Puerto Madryn, Argentina paused to take a closer look at some nearby whales, but got an unexpected surprise when one of the giant creatures lifted their boat onto his back. This is the footage they shot. Photo/Video: YouTube/Gisela Diaz

Canadian authorities, who have been hampered by choppy seas, were intending to resume their intensive search for Pillay on the weekend but the family is fearing the worst.

The popular 27-year-old was holidaying with his girlfriend Danielle Hooker and her family when the accident took place.

Hooker’s father was one of the five Britons who died when the boat went down.

“The situation is getting worse each day but the authorities are not giving up the search,” Raveshan’s father Mike told AAP from Canada.

“All we want to do is find Raveshan and take him home.”