Protestors from Greenpeace, the Wilderness Committee and No Tanks! gathered in Vancouver's Stanley Park Sunday to picket oil tankers off the B.C. coast, arguing it's only a matter of time before a devastating spill occurs.

The crowd met at Second Beach at noon for a lively rally, joined by a flotilla of supporters on the water -- including several of the original organizers of Greenpeace, which was formed 40 years ago this weekend in Vancouver.

Campaigner Stephanie Goodwin said locals would be shocked to learn how many tankers pass through right under their noses.

"The multitude of crude oil tankers going through the Burrard Inlet every week is the best kept secret in Vancouver and the best kept secret in British Columbia," she said.

Greenpeace says it's not a matter of if, but when a tanker will come aground or hit another vessel. But the oil industry says double-hulled vessels reduce the risk of a spill, and that their safety record is excellent.

New super-tankers carry more than twice the amount of crude that was on the doomed Exxon Valdez vessel, and two such tankers per week leave Vancouver now.

Greenpeace says that number is soon expected to jump to 10 tankers per week.

"It has quietly been increasing over the last few years … as California, China and other parts of Asia prepare their refineries," Goodwin said.

Whale watching skipper Simon Fawkes joined the protest because he fears crude from the Alberta tar sands – the kind that sprayed from a rupture in a Kinder-Morgan pipeline three years ago – would kill wildlife, as well as his business.

"I think the risk is too high for what we get out of it, which, if we're shipping crude oil to China, we really don't get anything out of it," Fawkes said.

While there have been a few small oil spills locally over the years, Greenpeace hopes we won't ever have to face a catastrophe like the one in the Gulf of Mexico – and says if we do, we can kiss our tourism and fisheries goodbye.

With a report from CTV British Columbia's Peter Grainger