Once that oxygen is in the blood stream, it’s circulated to the tissues and the reason whale muscle is so dark, almost black in colour, when you look at it, it’s very very darkis that it has myoglobin in it, that holds on to that oxygen, that turns it very dark and so you see more oxygen stored in these muscles than a terrestrial mammal would, so it doesn’t build up an oxygen debt as quickly as a terrestrial mammal would, so they can go longer without breathing in between.”