I was five, and I didn't know how to swim.
I had a lifejacket on, and we were having fun with the other people on the American River, so two other friends and I decided to "raid" their inflatable boat. When we got on, we also had a water cannon thing. We blasted everyone, then jumped off the ship. I was trapped between three inflatable boats, and it pushed me under the boat. I tried to swim down, but the lifejacket forced me up. Someone swam down and got me, and a few days later I learned to swim. I never wore a lifejacket even since.