I'd step away from that repair unless your willing to do it properly.
NEVER terminate a lamp tail below water level in a JB and especially a PC.
THIS INSTALL IS WAY BAD and YOUR promoting it by adding pool putty or silicone in the lamp conduit.
I'd remove the tail from the PC and extend it to a new JB higher than the water level, then run a switch leg back to the PC. This will be much easier than raising the level of the PC.

just my .02

See ya,
Kelly