It looks like a huge, above-ground pool, the kind you see in back yards from Parkville to Pasadena.
But instead of a bunch of children thrashing around in 4 feet of water, this pool is filled with 1.2 million gallons of water, and all the splashing will be done by three Beluga whales and five Atlantic bottlenose dolphins.
The National Aquarium's $35 million Marine Mammal Pavilion opened to the public yesterday, and instantaneous reviews -- ooohs and aaahs -- echoed through the huge, airy amphitheater.
"I can't believe it," said one woman among the 1,300 spectators to pack the 94,000-square-foot attraction on Pier 4 for yesterday's afternoon performance.
Before her eyes, two dolphins leaped into the air from their 22-foot-deep pool, spinning together in a way Olympic gymnasts can only dream of doing, before slicing back into the water.
"What if they jumped out of the pool?" asked one child.
"They won't," said the adult sitting next to him.
In all, some 4,400 people showed up yesterday for the water stunts of dolphins Nani, Akai and Nali. Sometime next month, the sleek, silver mammals will be joined in the pool by two more dolphins and a trio of Beluga whales.
One of the spectators -- 28-year-old Ed White of Charleston, S.C. -- said he gets to see dolphins just about every day back home. Still, he said, he wanted to "come see the fish" during a Christmas visit to his parents in Baltimore.
"They do more unexpected things than this in the wild," said Mr. White of the dolphins.
He said he regularly sees them near an island in Charleston's harbor. "I see them fight once in awhile; they slap each other around with their tails."
Unlike Charleston's harbor, however, the aquarium's 110-foot-wide pool is filled with tap water from Baltimore's waterworks. Add a little salt, some filtration devices and a handful of dolphins and -- viola! -- you've got a hot new ticket [$10.75 for adults] at the Inner Harbor.
"I think it's terrific," said Helen Naysmith, who in the past several years has brought her children and grandchildren to the aquarium from her home in East Nottingham, Pa. "When they [the dolphins] were jumping up in the air, I really got a sensational thrill. I could feel it."
Running the show for the noon crowd was Nedra Hecker, a 38-year-old mammalogist, who narrated over a microphone as video screens showed the audience how a dolphin's voice looked in a soundprint.
Ms. Hecker's presentation included a call for people to become involved in conservation, while the screens showed dead dolphins caught in plastic fishing nets.
"Conservation will be one of our strong messages," said Ms. Hecker, wearing a red and blue wet suit. "And that message will change depending on what's going on in the world."
During a week of grand opening events that run through New Year's Day, you might see the god of the sea walking around the new exhibit with a moldy green beard and holding a trident.
"I'm just glad to share the secrets of the sea with the people of Baltimore," he said yesterday. The first secret, said Neptune, was to tell people his name.
"Some kids were calling me Santa," he said.