Rob,
Our first step to finding a leak, is to let the water drain down until the leak stops...
Most leaks stop just below the skimmer, or the light, or a return..
If the leak stops just below the skimmer, then you can rule out a light or return leak.
I have never had any luck using a dye test.
If this was my pool, and I thought the problem was at the waterline tile, then in theory, once the water drained below the tile line, the leak should stop.
Thanks,
Jim R.