Gunite pools are a common choice because they are built to be irregularly-shaped, and are made with numerous materials such as concrete and stone. Over time, the pool can crack because of natural weathering or forced damage. Either way, you have the ability to repair the pool on your own without professional assistance.
Sweep away any loose dirt from the cracked area, using a broom.
Widen and deepen the existing crack, using the grinder. Attach the diamond blade to the grinder, place the grinder head in the crack, and then turn it on low. Move it up and down and side to side until the crack is a few inches deep and a few inches wide. The new size will allow the fresh cement mix to bond and harden more easily inside the crack.
Wipe away the gunite dust with a rag, and then soak the area with a hose to prevent the existing gunite from pulling moisture out of the fresh cement.
Combine three parts Portland cement, two parts sand, and one part water in a bucket. Use little water to begin with and add more until the mix is pasty but not dripping.
Line the walls and sides of the crack with the fresh mix, using a small putty knife. Fill the crack completely once it has been lined.
Remove excess cement and make it even with the surface, using the trowel.