Silly to say this but remember:
Water stops bullets MUCH better than people realize:
Most bullet will stop after just 5 feet, even if fired directly down into water. At an oblique angle maybe 90% of them will splatter, or simply richocet off the surface.
As long as they don’t hit you in the head when you come up for air, mostly you’re OK.
I think for most swimming away would have provided good protection.
The water is cold, gaijin. Hypothermia is an even greater problem for kids than adults because of the relatively small volume to surface area ratio as well.
I still remember being a young boy and getting a lesson on how water stops a bullet. My cousin shot a 22 long rifle out of a handgun into a water trough at a gas station (back when they had people that worked on your cars, this is maybe 1964) after betting a another kid it wouldn’t penetrate the 8 inches of water and even make a dent in the bottom. It didn’t.
PS: He did this right in the middle of our small town. Nobody gave it a second thought back then. Heck, we use to take our 22’s to school and store them all day in unlocked school lockers when we had firearms training after school.
Mythbusters covered this in one of their shows. The faster bullets all broke apart within inches of the surface. The most penetration was from the muzzleloader.
The Mythbusters proved this conclusively. Even a fifty caliber bullet shattered into pieces before reaching a target when fired at an oblique angle.