5 Best Bottom Paints: Anti-Fouling Coatings To Prevent Marine Growth

Picking the right bottom paint for your boat to protect the hull from underwater growth is very important for a number of reasons, including performance, efficiency and overall protection (not to mention environmental impact). Paint designed to prevent marine growth on a boat is commonly known as “ablative” paint or “anti-fouling” paint and re-applying fresh coats on your boat is an important part of regular annual boat maintenance.

There are a variety of different types of boat bottom paints that can differ widely in cost and durability. The main categories of bottom paint are also important to consider and there are many pro tips for getting the best results when applying the paint to your boat.

Types Of Bottom Paint For Boats

There are essentially 5 different types of boat bottom pain to choose from: ablative, hard modified epoxy paints, thin film bottom paints, water-based antifouling paints and aluminum bottom paints.

Ablative Bottom Paints

Ablative paint wears off slowly (i.e. “ablates”), exposing a fresh layer of biocides that make it hard for algae, barnacles and other marine growth to stay attached to the boat hull.

Hard Modified Epoxy Paints

These are paints that resist abrasion with higher copper content that offer better performance and hold up well for boats that are in the water for extended periods of time, or all year long.

Thin Film Bottom Paints

Thin film bottom paints dry very quickly, and can be applied rapidly in multiple coats. They have a slick PTFE finish and at least one biocide that prevents marine growth. Racing sailboats often utilize this type of paint.

Water-based Antifouling Paints

Water-based antifouling paints tend to be more eco-friendly and easier to apply with less dangerous chemicals. They make for easier DIY projects in the driveway or garage with less environmental impact.

Aluminum Boat Bottom Paints

Some bottom paints are specifically design for aluminum boats and can help owner avoid problems with galvanic corrosion that can occur when using other paints.

What is Antifouling?

Has your boat been getting slower and slower, and you can’t figure out why? Maybe your hull is coated in barnacles and algae, resulting in greater frictional drag. To make matters worse, manual cleaning under a submerged hull by divers for hire can be very expensive and difficult. Even if the vessel is pulled out of the water it can still be a challenge. The fact is, a fouled boat can burn up to 40% more fuel and reduce your boat’s speed significantly, as well as pose a host of other challenges to the safe operation and your surrounding environment.

Preventing Biofouling Marine Growth and Barnacles with Antifouling Solutions

Above: Barnacles growing on a boat’s hull underwater. Photo by Frans Van Heerden, Pexels.

What is biofouling?

Barnacles, algae, mussels and other marine growth have always posed as a challenge as they cause decreased efficiency and wear and tear thus reducing life span and corroding key components. This biofouling can creep into your boat, inside water intakes and pipes and cause blockages and downright mayhem.

What are antifouling agents?

Different approaches to preventing this issue include: electrolytic systems (that use a DC current to prevent marine life from thriving), chemical treatments/dosing (which can be damaging to the environment, and corrosive/unhealthy for the ship and its owners), ultrasonic (high-frequency waves that can reduce biofouling significantly) and finally electro-chlorination (which takes advantage of sea water to create chlorine that in turn kills marine growth).

What Are The Best Bottom Paints For Boats?

The best bottom paint for your boat will depend on your application and your environment, so do your research before diving in. Luckily there are various types of anti-fouling systems available for modern boats to help prevent marine growth and biofouling in different locations. There’s currently a movement in the marine industry for developing new, non-toxic anti-fouling solutions and methods. This often means less harmful biocides and copper replaced with other approaches. Below we’ve rounded up some of the best options on the market in various categories.

1. SLIPS® Dolphin™ Bottom Paint

SLIPS N1X Antifouling Boat Paint

Above: SLIPS N1x Performance Marine Coating paint from Adaptive Surface Technologies. Photo by Adaptive Surface Technologies.

Another great solution is advanced surface coatings like the SLIPS® Dolphin™ Bottom Paint (previously called “Foul Protect” and SLIPS N1x marine paint) available from Adaptive Surface Technologies.

SLIPS Dolphin is an entirely new kind of marine bottom paint for recreational and commercial boats of all sizes, and solves the persistent problem of biofouling. It creates an ultra-smooth, slippery surface that fouling can’t attach to. The paint lasts multiple seasons so you don’t have to worry about painting your boat every year. And unlike many existing products on the market today, SLIPS Dolphin doesn’ t actually contain any biocides and is environmentally friendly.

2. Hydrocoat Eco Paint from Pettit

Pettit Hydrocoat Eco is a water-based, copolymer ablative bottom paint, which wears away with use. It reveals a new surface and eliminates paint buildup. Hydrocoat Eco contains the highest level of the metal-free biocide called Econea which protects the hull but minimize negative effects on marine life. With a potent slime-fighting inhibitor, the formulation provides multiple seasons of protection. The water base makes this paint more comfortable to apply, and it cleans up with soap and water. It also lowers the amount of VOCs, eliminates the strong smell of solvents and can be thinned with water. There’s no need to sand between coats, and it will last multiple seasons depending on the environment. The copper-free formula is appropriate for any substrate including GRP, steel and aluminum. It will not lose effectiveness if the boat is removed from the water.

3. Interlux Antifouling Trilux 33

Anti Fouling Paint
Above: Interlux Antifouling paint “Trilux 22”. Make sure the anti-fouling paint you choose is formulated specifically for use on aluminum boats. Photo by Interlux.

One solution for antifouling paint is from Interlux, who makes a line of paint products developed for aluminum boats that is also compatible with fiberglass boats. The paints contain an additive marketed as “Biolux” that boosts the boat’s performance by controlling slime and preventing fouling, plus they are available in bright clean colors.

4. Clearline by ElectroSea

Another solution is from ElectroSea, a leader in marine growth prevention systems, who recently introduced the new Clearline system that contains patent-pending technology to help prevents marine growth and barnacles from forming in raw-water lines. This system utilizes electro chlorination technology to create an environment where barnacles, biofilm and algae will not be able to survive. This reduces required boat maintenance and extends the life of costly equipment, while also reducing the amount of harmful chemicals needed when performing scheduled, traditional “acid-descaling” practices.

5. JD Select Ablative Antifouling Bottom Paint

JD Select’s water-based formula is more environmentally friendly than conventional solvent-based bottom paints. But this doesn’t compromise its effectiveness, as its medium copper load keeps barnacles, slime, and weeds at bay in low to moderate fouling waters—often with just a single coat. Depending on the temperature, JD Select can dry in less than two hours.

Editor’s Note: This article was originally written in January 2020 and last updated in May 2022.