I sure hope it's not option 3. After the conduit goes down into the ground from the breaker box, it runs under concrete all the way to the light assy.

I have a steel fish tape long enough to do the job. It's just getting the old wire out that has me worried. There is a 8ga ground wire also inside the conduit. Getting a fish thru the conduit with the ground wire in there may be problematic. I didn't want to pull the ground wire out, but may have to. BTW, the pool is full of water. The house is on a low producing well so draining and re-filling is very expensive.