Horizontal cracking in your swimming pool around the top edge or in the tile line can point to beam shear, which occurs when the patio pushes against the top beam of the gunite pool resulting in a horizontal crack. The homeowner in this case had the patio replaced, and made sure to remove any water issue that could build up around the pool between the pool and the patio.
Next, This tile could be repaired, however the best fix is to remove, form a new layer to adhere the tile to, and replace the tile.
