A large portion of the deck is about 20x20, just above ground level. The three exterior lights are on three sides of the deck with the pool and higher levels of the deck on the fourth side.

I just got in from yanking up the old UF-B cables a few minutes ago. I was mistaken about the orientation earlier.

I have four circuits, each on a 15A GFI breaker.

1). Pool pump.
2). Auqaluminator.
3). Axillary outlet available from on the deck, about 12' from the pool.
4). Circuit for the three exterior lights, which are all more than 15' away from the pool anyway.

Also, I did find that there is a grounding rod at the circuit breaker near the house, so the wiring is not quite as bad as I thought. It was buried in some ground cover and I missed it when looking for it previously, but since I cut some of the ground cover away while digging up the UF-B, I came across it.

The UF-B was just below the surface of the grass, maybe two or three inches at most. I'm starting to dig the trench tonight. It's only a run of just over 16', so I should get it dug by tomorrow.