 Whales are adapted for diving to great depths . In addition to their streamlined bodies , they can slow their heart rate to conserve oxygen ; blood is rerouted from tissue tolerant of water pressure to the heart and brain among other organs ; haemoglobin and myoglobin store oxygen in body tissue ; and they have twice the concentration of myoglobin than haemoglobin . Before going on long dives , many whales exhibit a behaviour known as sounding ; they stay close to the surface for a series of short , shallow dives while building their oxygen reserves , and then make a sounding dive . 
