In ground fiberglass Spa developed a leak where the Spa light inserts into the shell. Water drops to half way down the light then stops which eliminates all other possibilities of the leak source (jets and water input above the light ... drain plus two other jet items below light). No cracks in fiberglass shell. Water leaks from within the Spa out to behind the light. Water drops from 2" to 1/2" per day until stopping half way down the light. Manufacturer says to use silicone to stop. Tried (by pool professional) ... applied plenty ... to no avail. Two local Pool Professionals say problem is in the niche which would require cutting into Spa shell and exposing the niche (concrete precludes any other method) to fix.

My problem is that there is a round hole in the shell that the light fits into; if you insert the light, then seal around the light, it logically should be water tight ... yet the silicone attempt to do exactly this did not work (maybe poor silicone job?).

Any recommendations would be appreciated.