By a school of small fish swimming fast in one direction. I knew there was something big and hungry chasing them so I started swimming frantically (actually just foaming the water and not really going anywhere). I was too afraid to look behind me. Eventually a barracuda swam by me and seemed to be pursuing the school. I was quite relieved to see it was only a barracuda (and a small one at that). Maybe I should have been more scared.

My friend on shore had no idea what I was doing. All he saw was flailing arms and frothy water. I imagine it was a pretty funny sight.