Tips From the Pros
How to... Remove Waterline Stains
Background - Waterline Stains

In case you've wondered what caused the stain in the first place, it's not industrial waste floating in the water where you dock your boat. It's algae. Gelcoat, the colored fiberglass exterior of your boat is actually quite porous. Since algae is microscopic in size, it gets into and attaches itself to these pores as well as to the surface of your hull. All that scrubbing and power washing that you did, got it off the surface, but of course you couldn't clean out the pores, they're too small.

Algae is the generic name for many thousands of species of primitive one celled or multicelled plants. They contain chlorophyll, the same stuff that makes grass green, and it's the chlorophyll that gives the stain its color. Green if the algae is alive, brown if it's dead.

Materials List:

Aurora Waterline Stain Remover
Plastic Paint Tray
Disposable, Plastic-Cored Paint Roller
Running Water (Garden Hose or Pressure Washer)

Aurora Waterline Stain Remover is a deep penetrating, professional strength, acid based cleaner enhanced with surfactants.

The active ingredients penetrate into the microscopic pores of your hull and clean them out.

Aurora's Waterline Stain Remover contains inhibitors making it safe for fiberglass, as well as brighteners to counteract any residual chlorophyll and help restore the original colour. The result: a clean bright hull.

Whay Others Say...

"Aurora Waterline Stain Remover is the best $#@* thing I have ever seen. It will be a cold day in hell before someone makes a product better than that. Worth its weight in GOLD."
B. Fee, Stoney Point Marina

"I have tried everything to remove a 3 year old waterline stain and nothing worked until your WATERLINE STAIN REMOVER. It did the job in 15 minutes!"
James T, Oakville, ON

"I'm amazed at how fast your Waterline Stain Remover got the brown stains out of my hull. I've tried everything over the past 4 years and thought I would have to live with the stain. You Boat Scrub is awesome stuff. My Boat looks new again. Thanks."
BW, Key Largo, FL

"My customer cleaned part of his hull with your Waterline Stain Remover and it was absolutely white. He ran out of product and asked if we could finish the job. We tried every other cleaner we had and cleaned it 3 times but the bottom still looked yellow next to the white area that he cleaned with your stuff. We would like to order. Our service guys are tired of dicking around."


First be sure to follow the instructions on the bottle. Remove heavy algae with a deck brush or pressure washer.

Pour Aurora Waterline Stain Remover into the plastic paint tray. Apply to stain with an inexpensive or disposable paint roller (Plastic Core roller recommended).

Wait 15 to 20 minutes. Rinse with garden hose. Repeat if necessary.

How the Pros Do It

Aurora Waterline Stain Remover has a sharp odour. When applying, start at the farthest downwind spot and work upwind.

Be environmentally responsible. Clean your boat on land sufficiently far away from the water's edge so that runoff will not enter the water.

To protect adjacent bottom paint from damage, protect by covering with masking tape and disposable Poly drop cloth or plastic garbage bags.