Fill a squeeze bottle with water. Add several drops of red food coloring to the water. Continue adding drops until the solution is a dark red color. This will make it easier to see in the water.
Put on a face mask and a snorkel. Inspect the area of the steps for suspected cracks. It may be possible that you can see the crack through your goggles and the food coloring is not necessary.
Shut down the pool filter. Wait for the water to become calm. Go underwater with your squeeze bottle and inject food coloring around the area of the steps. This may be a time-consuming effort; but when a leak is found, you will see the food coloring disappear into the crack where the leak is.