Harbor seal diving

 I got this video a while ago, while in Cordova, AK.  The harbor seal exhales through its nose before diving under water, in order to reduce its buoyancy.  Usually humans take a big breath before we dive, so we have extra oxygen, but the seals hold most of their oxygen in their body tissue, in the Myoglobin, and also in their blood, in the hemoglobin.  They don't need to hold it as a gas in their lungs, so they can exhale.  We don't have as much capacity in our body or blood.