Dives up to 10 minutes and longer have been seen, with the longest dive observed in the ocean lasting 12 minutes. Under experimental conditions, killer whales have made dives lasting as long as 15 minutes. All marine mammals have special physiological adaptations when they dive. These adaptations enable a killer whale to conserve oxygen while under water. A killer whale's heart rate can slow from 60 beats to 30 beats per minute while diving.
Marine mammals have a higher concentration of the oxygen-binding protein myoglobin in the muscles.
Myoglobin stores oxygen and helps prevent muscle oxygen deficiency. These combined adaptations allow a killer whale to conserve oxygen during a dive. This occurs because nitrogen becomes more soluble as pressure increases. Because it breathes at the surface, a killer whale is not inhaling air under pressure. And as a killer whale dives deeply, its flexible lungs collapse, forcing air into the windpipe and nasal ducts, where internal body surfaces cannot absorb nitrogen.