Flipper would have been proud.
There was Ric O'Barry, the guy who taught the legendary dolphin everything he knew, unfurling a protest banner inside the National Aquarium, telling the world that "Captivity Kills."
As surprised patrons filed out of the packed 3:30 show at the Lyn P. Meyerhoff Amphitheater, Mr. O'Barry and another protester quickly moved in front of the 1.2-million gallon tank where Nani and Akai had just finished their modern-day Flipper routine.
"These are disposable dolphins. They're all going to die in this fluoridated box," Mr. O'Barry told the audience as ruffled security officers at the Marine Mammal Pavilion tried to usher him out.
Mr. O'Barry was the trainer for the "Flipper" television series in the 1960s, but he has long since become an outspoken opponent of marine mammal captivity. He has been arrested a number of times, including during a recent protest at Puget Sound, Washington, where dolphins patrol the waters of a naval base to provide security.
The surprise appearance by Mr. O'Barry highlighted a two-hour protest across the street from the aquarium. As Baltimore police arrived to escort him out, protesters chanted "Boycott the aquarium."
Halfway through the show, the bottlenose dolphins staged an unusual boycott of their own. As trainers commanded them to leap and dive, Nani and Akai simply swam aimlessly around the tank, ignoring their baffled trainers.
"Sometimes a little noise in the pump room downstairs can make them do this," one trainer explained to the sellout crowd before the mammals finally got back to the business of entertaining.
Mr. O'Barry later insisted he had nothing to do with the dolphins' lapse in obedience.
The $35 million Marine Mammal Pavilion, which opened last year, has been controversial ever since the state of Florida threatened the aquarium with criminal charges for trying to capture dolphins in Florida.
The public display of marine mammals is legal for educational purposes only. The 25-minute aquarium show focuses on how the animals communicate, breathe and navigate, and it emphasizes environmental concerns.
"Awareness for problems of the planet has been heightened by the program," said Kathy Sher, a spokeswoman for the aquarium.
But animal rights groups insist the presentation is circus-like. They have targeted the growing number of aquariums nationwide with similar protests.
Patty Cockey, a spokeswoman for the Maryland Coalition for Marine Mammal Safety, said animals that swim 40 to 100 miles a day in open seas should not be confined to tanks. The aquarium's tank is 30 feet deep and 110 feet across. Dolphins live one-sixth as long in captivity, she said.
But the protesters' message seemed to bounce off tourists. Most said the mammals seem to be faring well.
"They're a lot better off here than in the ocean," said Bob Shearer of Reading, Pa. "At least they're getting three meals a day."