Spotted by Lisa - story of angry captive killer whale that kind of misses the obvious:

"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 stomach ache, according to marine mammal experts." Miami Herald: Orca returns to S.D. tank after attack »

... maybe the 5m-long whale, named Kasatka, got a little fed up with living in captivity?

According to one of the trainers,

"the animals perform as many as eight times a day, 365 days a year, 'so this, even though it can be expected because they are killer whales, it is definitely abnormal.'"

Hell, if I was performing at that kind of rate, I might be biting people too...

Defend the whales » (wild ones!)