The shark, shovel-headed, gunmetal gray and 8 feet long, cruised along the bottom of the tank, inches from the underwater window where 7-year-old Jake Gaffney had pressed his nose.

"I like the cool, sharp teeth," said Jake, of Limestone, Tenn., offering a bite-size review of the Pittsburgh Zoo & PPG Aquarium's newest exhibit: eight sand tiger sharks in a 16-foot-deep, 260,000-gallon tank where visitors can view the shy-but-scary predators from inside a 40-foot-long glass tunnel.

The zoo is promoting the grand opening of its shark exhibit today, hoping it will boost attendance at the Highland Park facility like its baby tiger and two baby elephants did last summer. The steady stream of visitors at the shark tunnel earlier this week was a good start.

"All the kids wanted to see was the sharks and polar bears," said Maureen Preston, of Mt. Lebanon, at the zoo with nephews Jake and Sean Gaffney.

"The last time we were here, he stood in front of the tank window for half an hour," said Christie Kohler of her son, Sam, 3, who seemed more fascinated with the fish than his sister, Anna, 5. "We finally had to make him leave. This is just his thing."

Allan Marshall, curator of aquatic life at the zoo's PPG Aquarium and Water's Edge, said he understands and shares the public's fascination with sharks.

"I started here at the aquarium seven years ago and since then the only thing anyone ever asked about was, 'When are you getting big sharks?'" Mr. Marshall said. "Well, we got big sharks and whenever anyone comes now they're just enthralled."

The zoo's sand tiger sharks, known as gray nurse sharks in Australia, where they are endangered, and as ragged tooth sharks in South Africa, are all adults and range in length from 6 to 8 feet. The largest in the exhibit tank, which was built to house walruses that the zoo cannot obtain, is named "Large Marge" and weighs 300 pounds.

All eight were caught on hook lines in August, three to four miles offshore from Ocean City, Md., by a commercial aquarium collector with a collection permit issued by the U.S. Fish and Wildlife Service.

The permit allows a limited number of the protected fish to be caught each year. They were caught with special circle hooks that are easily removed and designed to inflict minimum damage.

The zoo paid between $8,500 and $10,000 each for the fish, plus transportation from Maryland in a tank truck.

Their numbers in the world's oceans are declining due to overfishing, pollution, slow reproduction and poor survival. Female sand tiger sharks reproduce only every two to three years and carry their eggs inside their bodies, where the first shark that hatches eats the other eggs.

Sand tiger sharks can grow to 10 feet long and 450 pounds. With their prominent dorsal fin and mouthful of sharp teeth -- they swim with their mouths open and the teeth exposed -- sand tiger sharks appear fearsome and "sharky-looking," as one little boy in the tunnel said. But they are actually quite docile.

"There's never been an unprovoked attack by a sand tiger shark in the wild," Mr. Marshall said. "They will bite you if you pull their tails, but they won't attack humans even though they look like they could."