Adaptions
In the ocean harp seals can only last 15 minutes submerged, without coming back up
the reason that is true is because they need to protect them selves from lowering their heart rate to 90%.
Eye sight is very important to harp seal so that they can navigate.
When harp seals are born there lungs are fully adapted so they can swim it,
is natural for them.
Since harp seals are so used to swimming they will always have a normal flow of blood.