BALTIMORE, DEC. 26 -- The boosters of this city's Marine Mammal Pavilion, which opened today as a $35 million addition to the National Aquarium, like to tout their aquatic center as a stimulating, festive place, not as the subject of animal-rights controversies.

In fact, they consider the new pavilion so uplifting that they sent staff mammalogist Nedra Hecker on a "rocket ride" with a pair of bottlenose dolphins today.

Hecker's ride began when she dove into the pavilion's 728,000-gallon main pool and coaxed dolphins Akai and Nalu to put their snouts on the balls of her feet and push her around the tank. On cue, the three dove deep into the tank's 22-foot green waters until they turned and shot upward, the dolphins propelling Hecker 15 feet or so into the air.

The stunt was the highlight of the pavilion's inaugural show, and it drew applause, ooohs and aaahs from the crowd of 1,200. The show included demonstrations of dolphins doing flips, tail walks and swimming upside down. And one dolphin demonstrated his keen sense of hearing by retrieving rings while his eyes were covered.

The show was followed by a taped message dispassionately alerting people to things endangering wild dolphins: pollution, boat traffic and drag nets used for fishing.

"We wanted to make people ready for the message we wanted to give them. We want them to feel uplifted," said David Pittenger, the aquarium's senior director for programs.

Pittenger said aquarium officials are having trouble putting together a message that will rally people to the cause of conservation. For example, a film showing dolphins that had drowned in fishing nets was discarded as too graphic.

"We're really grappling with how we want to make that message," Pittenger said.

But some animal-rights groups have protested the use of the dolphins for show purposes. They say aquarium officials are sending the wrong message by taking the animals from their natural habitat and exploiting them for entertainment. A small contingent of protesters, kept to a distant street corner, made their feelings known briefly today as Mayor Kurt L. Schmoke and other dignitaries snipped a red ribbon to open the center.

"We believe that holding wild animals captive is unhealthy . . . and it takes away the animal's dignity," said Wanda Trimingham, a volunteer for the Sea Shepherd Conservation Society, which opposes the capture of dolphins.

Aquarium officials chafe at the criticism. They say the center's marine mammals are being cared for by a dozen trained wildlife experts. And they say the programs introduce marine life to people who normally would not come in contact with live dolphins or whales, helping them to appreciate the mammals.

"We're not interested in a circus show," program director Pittenger said. "We've had long, long discussions about the kind of show we want to put on here. People seem to think that what we are doing here does not go over the line."

Controversy over the use of dolphins and other marine mammals is only one of the problems that plagued the opening of the new center. Aquarium officials have been criticized for raising ticket prices to offset the cost of the new pavilion. Admission fees for adults rose $1.50, to $10.75. The fee for children 3 to 11 is $6.50; those under 3 still can be admitted free.

And the pavilion's opening was delayed for months because its main tank had to be redesigned, according to aquarium director Nicholas Brown. The aquarium's architect had hoped to make the tank out of giant sheets of clear plastic glass, but the plastic cracked under the pressure and some panels had to be replaced with other materials.

Construction also was slowed while construction crews tried to find a paint that would not peel from concrete portions of the tank, Brown said.

Brown opened the 1,300-seat amphitheater and 1.2 million-gallon saltwater pool complex by telling the audience that the new pavilion is intended to be a "bright and festive place" compared with its "dark and moody" next-door cousin, the National Aquarium. Both are in Baltimore's Inner Harbor.

"We want to transform {the pavilion} into a kind of theater," he said.

The pavilion can be reached by an enclosed, elevated walkway that connects it to the aquarium. Five times a day the pavilion's amphitheather will host a marine mammal show with three dolphins. It will soon include the aquarium's three beluga whales.

Schmoke met his first dolphin today when he and his daughter were invited to step on a shallow ledge in the tank to touch one. Schmoke declined an offer to go swimming and follow in the tradition of Gov. William Donald Schaefer, who as mayor took a dip in the aquarium's seal tank.

"I don't have a rubber duck," Schmoke quipped.