How long can a killer whale hold his breath?

About 15-20 minutes underwater and it has to go back up to get air
The Killer Whale is the fastest mammal in the seas. It can swim up to thirty five miles per hour. While swimming rapidly it can often make leaps forty feet long , rising four feet above the water. The Killer Whale is capable of diving to depths of over 1000 feet and it is able to remain beneath the surface for as much as twenty minutes.
Killer whales can hold their breath upto 15 minutes by slowing down their beats from 60 beats to 30 beats per minute while diving.