Earlier this week we uncovered our above ground pool. Our pool was installed last year so this is our first attempt at getting a pool ready after winter. It had green algae but we shocked the pool and the algae is gone. We are in the process of getting clear water instead of cloudy water. Just today I noticed stuff around the water line. We scrubbed the stuff and it is thick and greasy. The only way to remove it from the scrub brush was with dawn soap. This is only located at the water level. If you feel down the sides of the pool this is not under the water. Does anyone know what this is???