Relax Spa Waterline Cleaning Gel has been formulated to remove 'tide marks' found above the waterline on spas and pools. It's non-abrasive, low foaming properties are ideal for all surfaces, including acrylic spas. Using a Gel as opposed to a conventional liquid product will ensure maximum contact with the surface to be cleaned. Use above the waterline using a sponge or soft cloth and leave for 10 minutes before wiping away.