A couple of observations:
First, it reminds me of the pools on containerships.
But rust is not that big of an issue, with the right coatings. The above pool is on a 30 year old ship, and is filled with seawater. The paint is regular hull paint, which we have in large quantities in light blue. If you wanted to do it right,there is also a ceramic coating that we use in fresh water tanks, which is sprayed on and will not rust unless damaged. But this pool uses regular two part epoxy. http://www.hempel.com/en/products/hempadur-45143
The containers that they use for the pools do have corrugated sides, and can probably take the pressure with no problems. Most of the strength is built into the pillars at the four corners, which can take having five more filled containers stacked on top. The perimeter edges are also reinforced, so as long as you don't compromise those, you should be fine.