You are well adapated to the crushing, lightless depths of the deep ocean.
Prerequisites
Elemental Bloodline (Water Elemental), Aquatic Adaptation, bloodline level 1st.
Benefit
The damage you take from deep water pressure is reduced by 1d6 for every two Elemental Feats you possess, and you take no damage from very cold water.
In addition, you can see twice as far as normal through clear and murky water. While underwater, you gain darkvision out to 60 feet or increase your existing darkvision by 60 feet.