In Aquaman, When the Father/Son Pirate team thought they were going to drown, why didn't they put on their (scuba) re-breather units?
While it is true that their gear (scuba/re-breather suits) would have helped them breathe for a while, it was not a viable long term solution. Eventually they would have run out of oxygen. Even before that happened, they would reach such depths under which the suits would no longer function and they would be crushed by the pressure of the water. Typically this happens somewhere around 1000 feet.
Given this, the father had to take a call and make his son leave and save himself.