Be afraid. Be very afraid of the monsters lurking in the inky, icy depths, the husband and wife were warned.

"These animals are going to hold you with their giant flippers and tusk you and suck your brains out," filmmakers Sarah Robertson and Adam Ravetch were cautioned by the Inuit when they asked about going into the Arctic water to film walruses.

"The monster story, really, we thought, sort of mythological monster story, even," Robertson said. "But it showed how scared they were of these animals, and science didn't know very much about these animals."

So, she and Ravetch, specialists in underwater cinematography, decided to build a walrus-proof cage. But how big should it be, they wondered.

"We went to the Los Angeles Museum of Natural History and we took a tape measure out and we started measuring the big stuffed walruses they had there," the co-director of "Arctic Tale" said in a recent phone call.

"We took this cage up north and started diving underwater and taking some of the very first images of these animals underwater." Once beneath the surface, though, the couple saw behavior that was far from monstrous.

"That's when we started to see tactile, gregarious, social animals that really needed to be with one another all the time. We saw the mother holding her little calf so human-like, and then we found the nanny walrus, the helper walrus. This was stuff never really known before. ... That's sort of how it went over 15 years, just constantly discovering new things."

The couple eventually shed the cage but later learned there are walruses who live in very deep water and cannot eat clams like their brethren. They capture seals in their flippers and use their vacuum-like mouths to suck the meat from their prey.

You won't see that in "Arctic Tale," a G-rated film tracking a polar bear named Nanu and a walrus pup called Seela from birth to maturity and sounding the alarm about global warming. Steering the moviegoers is narrator Queen Latifah.

"I thought that it should be a woman to tell the movie, because it's such a maternal story," Robertson said. "We also were looking for a comedian to try to lighten up the movie a bit and to carry the comedy, the light moments that we were trying to write into the movie, and she's very accessible to a young, new audience."

If you sit through the credits, you will learn that many animals actually "play" Nanu and Seela.

"They're composites. It would have been impossible to track the same animals over eight years, which is the duration of the story. So, they really represent many, many different walruses and bears we encountered.

"For us, they represent the best of their species; they hold the best qualities of bear and walrus, and all the sequences are inspired by totally our own experience and observation and by science, what is happening to these animals."

The movie tracks animals for eight years but gestated for nearly twice that long.

"This really represents 15 years of our work in the Arctic. Back then, we didn't know we were making a movie, 'Arctic Tale.' We were more like starving young photographers trying to find a niche in the world for ourselves. We were underwater specialists and wanted something different.

"I'm a Canadian, so going to the Arctic wouldn't be so unusual. The Arctic sort of lives in the Canadian psyche more than for other people," said the Toronto native now living with her family on Vancouver Island.

"We went up into the Arctic and started finding animals people didn't know very much about -- the walrus definitely was one of them."

Walruses eventually led to polar bears, who may be the new penguins in terms of popularity, but are still huge, smart predatory animals that "get your heart rate up," Robertson said.

"We didn't want them to come close to us, but they do. They're very curious and they want to check you out, they want to sniff all your stuff and know who you are, but they do come close and you have to set up boundaries and set a territory around your camp," to draw a line in the snow.

Like cops waiting for suspects or paparazzi for celebrities, the couple and the small crew they sometimes hired spent time on stakeouts, poised for action.

"You never know when it's going to happen, so you have to be awake from 4 in the morning till it gets dark. That could be around midnight or 1 o'clock in the morning. ... You can't move and you have to look at the scene and wait and be ready. My husband has sat on these stakeouts for months at a time doing that. By himself, sometimes totally surrounded by predators."

But the stakeout produced images of polar bears going into a herd of walrus and learning to hunt, plus what followed.

"We had no idea we'd have these female walruses going back up on the [island] rocks to try to save these calves. We had no idea we'd be seeing that, so that was just awesome when we saw that sort of devotion."

Robertson and Ravetch, parents of a 12-year-old son and daughters ages 6 and 5, can understand that devotion. Their children often travel with them, and the filmmakers try to hire Inuit with children who can be playmates for their offspring.

The movie, getting a boost from Starbucks with in-store promotions and discussions about climate change, closes with a warning that the Arctic could be ice-free by 2040. It also features children offering tips on combatting global warming.

"They are the ones who are going to be making the hard decisions and hard responses, but that's why I don't think our movie's a doomsday movie. I think it's actually quite a hopeful movie, it's a celebration of these animals' capacity to carry on, to make new choices, to have the courage and the will to survive," Robertson said.

"I hope kids will be inspired by that. If the bear and the walrus can do it, so can we."