What kind of a pool is it? Also, do you have any idea where the leak is? In the plumbing, shell/liner, etc. I can't imaging any 'miracle goo' that would be able to plug any kind of a leak considering the dilution it would go thru while finding its way to the leak. Best thing is to find it and fix it permanently. Depending on your answers to the above questions there are lots of ways and tricks to finding and repairing leaks.
Al