How do I stop my Pool Leaking?

Question:I have a 3 metre x 3 metre x 75cm pool in my garden.
Its one level, and tiles inside and out. However, it is leaking.

It has NO plumbing, NO filters, NO inlets/outlets... its just like a great big tiled box.

I have used tuffmix pool puty on some obvious bits where grout is missing, and where bubbles come up where I tread, and all seems fine, but the whole thing is covered in tiles 15cmx15cm... It would cost me about £25K to coat every joint in epoxy pool putty, so I was wondering if there is another way??

Is there some see through rubber pool paint? or a latex fluid I could coat the thing with that wont cost me my house?

It was supposed to be a bit of fun, which has turned out rubbish. So much work has been involved, and I really want a quick inexpensive solution. I cannot see evidence of where any leaks are... but there must be lots of them.

Is there something like RADWELD for pools? That would be cool...

Any ideas folks?

Answers:
Do you have to see the tiles? If not, I would find a garden store that sells pool supplies, and ask for pond liner. Here in the US, we use a heavy rubber/vinyl sheet for the bottom of ponds like this. It's thick, and waterproof.

You could dig out around the outside of the existing box, put a piece of liner inside the box, and fold the extra over the outside. Then backfill on the outside to hold the liner in place. The stuff is dark grey or black, though, so you won't see any decorative tiles, but it WILL hold water.