A killer whale was back performing before crowds at SeaWorld Adventure Park only a day after dragging her trainer to the bottom of the pool.

Kasatka, a 5,000-pound-plus female, grabbed Ken Peters by the foot and tugged him underwater for less than a minute, surfaced, then took him down for another minute before he managed to coax her into releasing him Wednesday.

The drama took place just before the finale of a show at Shamu Stadium that would have involved the whale rocketing into the air from underwater and Peters diving from her nose. They had performed the stunt together many times.

On Thursday, the 39-year-old Peters underwent surgery for a broken left foot but was otherwise in good spirits, said Mike Scarpuzzi, the vice president of zoological operations at SeaWorld San Diego.

Kasatka was back in the water for a lunchtime performance that went off Thursday without a hitch. Trainers limited the performance to tricks that did not involve getting into the water with the orca.

Trainers from the San Diego park and sister parks in Texas and Florida will review Kasatka's behavior before the incident and try to figure out what happened, Scarpuzzi said.

Some experts said the 30-year-old orca simply may have been having a bad day.

Kasatka may have been put out by a spat with another whale, grumpy because of the weather or even just irritable from a stomachache, they speculated.

"Some mornings they just wake up not as willing to do the show as others," said Ken Balcomb, the director of the Center for Whale Research in Friday Harbor, Wash. "If the trainer doesn't recognize it's not a good day, this will happen."

The Humane Society of the United States, which opposes keeping orcas in captivity, issued a statement Thursday suggesting SeaWorld may one day have to kill a whale to save a person's life.

"Simply put, keeping these powerful and intelligent marine mammals in captivity and allowing people to swim with them is utterly inappropriate," said Naomi A. Rose, marine mammal scientist for the society.