i don't know where you want to put your swimming pool?? If it is in a garden then I would cut out the bottom so I would have drainage but contain the plants.

If it is free standing on a deck or something of that nature then you would surely need drainage holes.

Don't know why that would not work it you have drainage so they are not sitting in soggy soil and they are not too crowded.
Interesting idea.

Try the container gardening forum...I bet someone's done it.