It's probably something like water in the j box for the light. The last time I rewired a pool light the cord that came with it was 25' or so.
If you've got an air compressor sometimes you can have someone use a blowgun in the conduit and listen for the air coming out.
Maybe its a dumb question but are you getting power to the bulb socket and have you verified the bulb is good? Sometimes those sockets corrode