How to replace lighting cabling thats stuck in the ground

[jake118822]

Hi all,

I moved into my new house 5 months ago and am now finding the problems I've got with the pool.
Both of the pool lights, 1 in the pool and 1 in the spa, don't work. Probably because the transformers they were wired to literally exploded in half.
I've bought new lights to go in the pool but the issue I have is with the cabling.
I've checked the continuity of the cabling and 1 is completely worthless but the other 1 is useable. My problem is that both wires just go straight into the ground with no conduit around them. I've dug down over 50cm and its just compacted dirt around them.
Ideally I would want to replace all of the cabling before fitting the new lights.
My question is this: Does anyone have any experience of replacing faulty cabling that doesnt run through a conduit? If i go ahead with replacing it, is my only option to dig a new trench around the pool and then down to where the cabling will need to run to the light in the side of the pool?

Any help, advice, pointers, pictures or videos people could share would be brilliant.

Cheers
Jacob