http://www.canine-hydrotherapy.org/Or a pool from here. I now won't use any pool that is not registered with either of the associations mentioned, regardless whether it is for fun or rehab. They will have rules and regulations to follow which means it is safer for the dogs all round. Yes it does mean a quick call or fax to your vets, but its a clearence to say there is nothing wrong with your dog and its fit and well currently as far as they are aware.
They will be full insured if anything happens.
Also they will have to of gone through a qualification and not just be any random person setting up a pool..