Thought, "Figure this out or die. This very second."
Remembered my lessons on floating, got my lips above water and took a sip of air. Stopped fighting, floated back up, did it again. After 3 or 4 tries, I had enough air to calm down, lay on my back and breathe. Just dandy after that. Went home, got laid, and here I am typing this dumb comment 30+ years later.
When I was a pre-teen I was trying out a Boogie Board and a wierd current pulled me much further out into the ocean with much more force than any of the other waves, but years of swim lessons had me more focused on finding upward and trying to stay in place than panicking so I got dumped back onto the beach conscious instead of needing the lifeguard to drag me out