Cool off from the summer heat by building your own concrete wading pool. Choose a location that is partly shady so the water stays cooler. Make sure the location isn't in a low-lying area. Runoff into the wading pool will make it muddy, and fertilizer and pesticides could get into the water. Choose a day that's cloudy and cool to keep you cool and the concrete from setting up too fast.
Dig a hole that is 4 feet by 4 feet and 2 feet deep. Check the bottom and sides to make sure they are level. Check that the edges of the pool are level by laying a piece of scrap wood from one edge to the other and laying a level on the wood. Outline the hole with cement blocks stacked three high. Add a 4-inch layer of gravel to the bottom of the hole.
Pour 2 inches of concrete into the bottom of the hole. Tamp down well. Lay the metal reinforcing mesh into the hole on top of the wet concrete. Pour another 2 inches of concrete on top of the mesh, completely covering it. Any exposed mesh will rust and leak water through the cured cement.
Place reinforcing metal bars in the holes of the cement blocks. One bar in every other block is enough. The bars should be slightly below the top of the holes. Fill the holes with cement.
Cover the cement with plastic sheeting and let it dry for 24 hours.
Apply a rendering coat made of three parts sand to one part Portland cement mixed with water no more than 48 hours from pouring the concrete. Exactly how much water depends on the moisture in the sand and the humidity in the air. Add a little at a time until you get a consistency of frosting or toothpaste. Add a waterproofing product per label directions to the rendering coat. Spread the rendering coat over the bottom of the pool and up the sides with a trowel. This coat waterproofs the cement and also adds a smooth coat so the cement won't be rough on feet or legs.
Lay plastic over the pool and keep shaded if the weather is hot. The concrete should set to cement within five days and be ready to fill with water.