Digging Under Pool to Get to Leak

[wazzjazz1]

We had someone in who was able to pressure test and find where the leak in our inground vinyl pool was. It is just below the skimmer. We opted to dig the trench ourselves rather than pay the pool people to dig it for us. They will then do the repair. The problem we are having is the 3 feet of gravel that is all around the edge of the poool. No sooner do we start digging, more gravel begins to fall into the area we just emptied.

How do we get it so the gravel doesn't keep filling our hole? We have to go down another 8 inches.