Choosing which bottom paint to use is a job just about every boat owner has to tackle. Most of us weigh up things like price, color, ease of application, durability, and how well it works against growth, but there’s another factor that is starting to get more attention; the impact on the marine environment.

Why copper is a problem

Today, most conventional antifouling paints rely on copper-based compounds, such as cuprous oxide, to be the active ingredient.

Copper is a strong biocide, creating a toxic barrier that helps prevent marine growth. The downside is this same toxicity affects more than just slime and barnacles, it seeps into surrounding waters where it can harm delicate ecosystems. The rate of seepage depends on the type of antifoul, age, how it’s cleaned and the frequency of cleaning.

When the copper levels in the water get higher, it disrupts algal growth, which sits at the foundation of the food chain. When algae populations decline, everything above them – zooplankton, fish, shellfish, even marine mammals – feel the pinch. Studies on salmon have shown that copper exposure can disorient the fish, interfering with their senses and making it harder for them to migrate, feed, or avoid predators. In short, copper may keep your hull clean, but it doesn’t necessarily leave the water around you in the same condition.

Growing restrictions worldwide

Because of the environmental concerns, some ports, marinas and governments in different parts of the world, have already begun restricting in-water hull cleaning for copper-based antifouls.

In the United States, the National Recommended Water Quality Criteria established under the Clean Water Act, sets a limit on the amount of copper that can be present in marine waters. It’s possible for this amount to be exceeded as copper accumulates in poorly flushed basins, or crowded marinas. Areas of the Port of San Diego were found to have exceeded the copper limit, leading to the introduction of a Copper Reduction Program, which included more stringent regulations on hull cleaning. Washington State already has the legal framework in place to ban the sale of new recreational vessels with copper antifouling, and the sale or application of antifouling paint with >0.5% copper – they just haven’t enacted it yet.

Over in northern Europe, Denmark recently expanded their list of banned antifouls for private yacht owners with boats under 24 meters (78.7 ft), to include products like Hempel’s Mille NCT 7173A (cuperous oxide), and Hepel Hard Racing TeccCel 7679C (copper thiocyanate). Close by, Norway is implementing new regulatory frameworks and biofouling controls, after concerns about elevated contamination levels, including copper, in areas like the harbors of the Oslo Fjord.

Are copper-free antifouling solutions effective?

For years, the main criticism of copper-free antifouls was that they simply didn’t work as well. That reputation still lingers, but recent developments are beginning to prove otherwise.

For now, alternatives to copper antifouling include:

• Foul-release coatings
• Foul-release wraps
• Hydrophilic coatings
• Non-biocidal coatings
• Ultrasonic antifouling
• Natural enzyme-based solutions

Which one would be right for you would depend on your boat, budget, cruising plans and grounds, and personal preferences.

The cost of going without antifouling

One option that’s not a real solution is skipping antifouling altogether.

Having a heavily fouled hull doesn’t just slow you down; the increased drag causes the engine to burn more fuel when motoring, which drives up emissions. Research has shown that boats with untreated growth can use up to 40% more fuel than those protected with antifouling. This results in more greenhouse gases being released into the atmosphere, not to mention the cost of wasted fuel.

Making more environmentally friendly choices for now

The reality of cruising is that copper antifouling may be the only practical choice in your area. That said, you can still reduce its impact by:

• Selecting paints with a lower copper content
• Managing the removal of old antifouling responsibly
• Applying new paint carefully
• Storing or disposing of leftover antifoul paint in a way that prevents accidental environmental contamination
• Avoiding unnecessary in-water cleaning that releases concentrated bursts of copper into a marina or poorly flushed body of water

If you’re using a contractor to repaint your antifoul, it’s also worth asking them how they manage the environmental side of things.

Looking ahead

Regulations, environmental pressures, and new technology are all moving the antifouling conversation forward. Ten years ago, copper-free paints were niche. Today, they’re becoming more viable. In another decade, they might be the norm.

For liveaboard cruisers the takeaway is simple; every choice we make has an impact. From the way we provision to the coatings we put on our hulls, there are more and less sustainable choices. By staying informed and considering alternatives, we can help ensure the waters we sail in remain as healthy and inviting as possible.

Remember, the small, positive impact of one boat is multiplied when others do the same.

noforeignland is all about discussing ideas and sharing information respectfully, for the benefit of the wider sailing community.

If you’ve had an experience with an alternative antifoul, be sure to share it down in the comments! While it’s not right for everyone, you might just help make other cruisers next antifouling choice clearer.