When I was about 9 years old we had a swimming hole that was about 3 feet deep and probably 20 feet in diameter...just a natural "wide" spot on a small creek. It was very cold even in the dead of summer because it was shaded its entire length....really perfect for a swimming hole. We decided, as boys will do, to build a rock dam across that creek. There were LOADS of flat rocks about the size of a concrete block but about 1/2 of the height...theyd be fieldstone at Home Depot. We stacked those things acrosss that creek and abount 6 inches above the water. Of course it leaked as much as it didn't but with a couple of days that hole as 6 inches deeper and about 10 feet bigger in diameter...so we decided that if that worked we would stack them about 3 feet high. The water started rising slowly but again it leaked as much as it didn't.....then we have a couple of days where it rained about 10 inches and when we were able to go back we had built a sizeable swamp...that dam had overflowed a sizeable portion of the homeowners adjaceny pasture....the pool had gone from about 20 feet in diameter to about 100 feet long and about 40 feet across before it hit the cut banks where the water depth was about 3 feet deep and in the middle it was about 6....shortly after this the owner discovered our "dam" and brought a back hoe and scooped out what he could at the dam and laid it down stream and up on the downstream side of the dam. Stopped most of the leaking. He then removed a place just above a large piece of granite that allowed all of the water to leak to one side...and used the area beneath the dam as a road across the creek. By the next summer that side where the water ran was about 15 feet deep and about 15 feet wide with a shelf about 6 feet deep...he put up a rope swing and even a diving board...it was the PERFECT swimming hole...it can be seen on google maps to this day at 34.08956858421145, -84.8920353339019.