It just might be the happiest whale tale since Free Willy: a pair of grey whales stranded on the low-tide mudflats of Boundary Bay in B.C.'s Lower Mainland have escaped.

A rescue effort sprang into action Friday afternoon after the two whales — a mother and a calf — became beached near Centennial Park in Boundary Bay in Delta about a 40 minute drive south of Vancouver.

Fisheries and Oceans Canada led the effort with refloatation devices — large, inflatable airbags to lift the animals up — and a vessel. The Vancouver Aquarium was also on scene to handle any medical setbacks the animals may have suffered.

"It's absolutely fantastic," said Martin Haulena, the Vancouver Aquarium's head veterinarian. "A very, very good ending."

Haulena said the animals got stuck at approximately 2 p.m. PT. They were freed by about 6:30 p.m.

Fortunately for them, the tide was coming in to help their escape. A cheer rose from about 100 assembled onlookers as the whales began to move freely, flapping their fins.

Watch as the whales begin to right themselves in the rising tide:

After being stranded for much of Friday afternoon, a grey whale and her calf start to right themselves in the rising tide of Boundary Bay. 0:34

Dangerous position

Haulena said Boundary Bay — a wide, shallow bay straddling the Canada-U.S. border — is a place where grey whales could easily get stranded.

He described the animals as bottom feeders: they skim along the ocean floor filtering organisms from the sandy bottom through their mouths. He thinks they were likely foraging when the tide went out and became stuck.

As the tide rolled in the whales began to flap their fins and get free. (CBC)

Once out of the water, he continued, their large bodies put them in danger.

"They were never designed to bear weight," he explained. "That can compress their lungs. They can't breathe right. Their circulation gets very altered ... it's a very big deal potentially."

He added that the whales are not out of the woods yet.

If they were injured too severely by their ordeal, they may still die.

Rash of beachings

Friday's dramatic scene is one that has been happening all over the west coast of North America this year as an unusual number of grey whales have become stranded and died on their migration from their southern calving waters in Mexico to their northern feeding waters.

Some researchers are pointing to a lack of food as the cause.

Haulena said beachings tend to happen cyclically, with some years being worse than others, but agreed the population may be exhausting its food sources.