San Diego ? Some days, killer whales just wake up on the wrong side of the pool.

A 2 1/2-ton orca that dragged a trainer underwater during a show at SeaWorld may have been put out by a spat with another whale, grumpy because of the weather or just irritable from a stomachache, according to marine mammal experts.

“Some mornings they just wake up not as willing to do the show as others,” said Ken Balcomb, 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 whale, Kasatka, was back in the water Thursday for a performance that went off without a hitch. But the show was limited to tricks that did not involve trainers getting in the water.

Meanwhile, experts from other SeaWorld parks and marine centers converged in San Diego to review Wednesday’s incident and figure out what set the whale off.

Killer whale Kasatka leaps out of the water while a trainer signals Thursday during SeaWorld's Shamu show in San Diego. Trainer Ken Peters remains hospitalized after suffering a broken foot when Kasatka dragged him underwater twice Wednesday.

The trainer, Ken Peters, 39, underwent surgery Thursday on a broken bone in his foot but was otherwise in good spirits, said Mike Scarpuzzi, vice president of zoological operations at SeaWorld San Diego and a former killer whale trainer.

Kasatka, a 30-year-old orca that is about 17 feet long and weighs well over 5,000 pounds, twice held Peters underwater for less than a minute each time during a show at Shamu Stadium.

The act called for the orca to leap out of the water so Peters could dive off her nose. Instead, as several hundred spectators watched, Kasatka grabbed Peters’ foot in her mouth and dragged him toward the bottom of the 36-foot-deep tank.

When they came up, Peters tried to calm the animal by stroking its back, but it grabbed him and plunged down again. The whale finally released him and Peters was able to surface and swim away. He emerged with one leg of his wet suit torn.