My relative has a pool like mine - inground with white plaster - and it had a leak we could not locate so a leak detector company was hired. After checking the entire pool inside and out and performing pressure tests on all plumbing, they determined the leak is from hairline cracks in the plaster on the pool wall. He showed us with an eyedropper of dye at the crack how the dye was bring sucked right into the crack. He advised using A+B putty or a similar product for sealing leaks underwater and test with dye after performing the patches. He said sometimes the patch will last days and other times it will last years, and a more thorough fix would be to get the plaster replaced, but for now patching will work. I wanted to share with others who might experience a leak they can't find. I was impressed with the leak detection process - it was educational.