Canada's most famous animal-rights advocate is celebrating her birthday by getting naked for an orca named Corky.

Pamela Anderson turns 52 today, on Canada Day, and she's distressed about Corky having to live in a concrete tank at SeaWorld for 50 years.

The marine mammal was captured off the coast of B.C., not far from Anderson's hometown of Ladysmith on Vancouver Island.

So to draw attention to Corky's fate, she's written a letter to SeaWorld CEO Gustavo Antorcha, announcing a new ad campaign by People for the Ethical Treatment of Animals.

The campaign demands that Corky not spend the rest of her days "in a tank that, to her, is comparable to the size of a bathtub".

Anderson, a former Playboy model and Baywatch star, removed her clothing for the ad.

“We’ve been fighting against SeaWorld for a long time because obviously captivity is not something that anybody’s comfortable in, especially whales that swim a hundred miles a day,” she says in the video. “I can’t imagine a wild animal being happy in an enclosed environment.”