How long can you hold your breath under water?  Humans can go without breathing for about 2-4 minutes.  Seals can hold their breath for about 90 minutes, and some turtles can stay underwater for about 10 hours.

Why can the seals hold their breath for 90 minutes and still stay alert and hunt?  Scientist have found that certain animals–including dolphins, whales and sea otters–appear to be protected by elevated levels of oxygen-carrying proteins in their brains.  This discovery could help doctors and researchers understand stroke victims and our brain aging process.