Every spring I find myself standing in a French boatyard, mask on, sanding block in hand, wondering why I am about to spend a small fortune painting poison onto my own boat. Antifouling is the one job no cruiser escapes, and it is also, quietly, one of the most environmentally loaded decisions you make. The paint that keeps weed and barnacles off your hull works by leaching biocide into the water you are floating in. The more I learned about what that biocide does, the more I started questioning the default.
Here is what I have worked out, after several seasons of hauling out on both French coasts, about the choices and their consequences.
Why antifouling is a pollution problem at all
The job of antifouling is to be toxic. That is the entire mechanism. The paint releases a biocide slowly into the surrounding water to kill or repel anything trying to grow on the hull. In a busy marina with hundreds of boats, that biocide accumulates in the sediment of an enclosed, poorly flushed basin, exactly where it does the most harm to the life on the bottom.
The history here is instructive. Tributyltin, or TBT, was the wonder biocide of the 1970s and 1980s until it turned out to be devastating to shellfish at almost undetectable concentrations. It was banned for leisure craft first, then prohibited entirely on the hulls of sea-going vessels by 1 January 2008. The lesson stuck: a biocide that works brilliantly can still be an environmental disaster.
Copper is the default, and the next thing under scrutiny
What replaced TBT is overwhelmingly copper. Around 95 percent of antifouling coatings now use copper or cuprous oxide as the active biocide, and cuprous oxide formulations protect an estimated 90 percent of the world's fouling-protected hulls. Copper has been doing this job for over a century.
The trouble is that copper is the next biocide drawing regulatory attention, for the same reason TBT did: it builds up in marina sediments and harms non-target marine life. Several jurisdictions have already moved to cap copper leach rates or restrict copper paints outright, and the direction of travel in European waters points the same way. If you are choosing a paint to last several seasons in France, it is worth assuming copper rules will get tighter, not looser.
For the practical side of repainting in France, including what yards charge and the rules they enforce on collecting your sanding dust, I keep a separate guide to antifouling rules and costs at a French yard.
It helps to picture where the biocide actually ends up. A typical cruising yacht of 10 to 12 metres carries a wetted surface of roughly 25 to 35 square metres below the waterline, and a self-polishing copper paint is designed to wear away over a season so the biocide keeps leaching. That means a good fraction of every tin you roll on does not stay on the hull at all; it dissolves into the water over the months that follow. In open, well-flushed water it disperses. In a marina basin, where the same enclosed water sits with hundreds of other hulls, it concentrates in the mud on the bottom. That is why marina sediment, not open coast, is where copper restrictions tend to bite first.
The lower-impact alternatives, honestly
There is no perfect antifouling. Every option is a trade-off between effectiveness, cost, hull material and your conscience. These are the realistic choices.
Copper-free biocidal paints use alternatives such as Econea (tralopyril) or zinc pyrithione. The headline figure that sold me on looking harder: an antifouling made with just 6 percent Econea can be as effective against barnacles and mussels as one with 50 percent copper. They cost more per tin and the technology is younger, but they take copper out of the equation, and they are essential anyway if your hull is aluminium, where copper paint causes galvanic corrosion.
Foul-release coatings, the silicone-based slippery films, contain no biocide at all. Nothing grows because nothing can grip. They suit boats that move regularly and clean up with a wipe, but they are expensive, fussy to apply, and a poor choice for a boat that sits still all summer.
Hard, low-leach coatings sit at the durable end of the copper family. A hard antifouling holds its biocide in a solid matrix that releases slowly and survives a grounding, which suits the drying harbours of the Channel and Brittany. It still leaches copper, but a good one leaches less.
The fourth option is to use less paint and more elbow grease: keep the boat moving, dive and wipe the hull through the season, and accept a thinner, gentler coating. This is the approach that genuinely cuts your footprint, and it pairs naturally with the wider habits I describe in my notes on low-impact anchoring to protect wildlife.
Match the paint to your French cruise
The right answer is not the same on both coasts, which is something visiting boaters often miss.
On the Channel and Atlantic side, the tide is the deciding factor. If you keep the boat in a drying harbour in Brittany or Normandy and she sits on the mud twice a day, a soft self-polishing paint scrubs off on the bottom and a hard, abrasion-resistant coating earns its keep. The water is cooler and the fouling pressure is lower than the Med, so a single season between coats is realistic.
On the Mediterranean side it is warmth and standing still that drive growth. Summer sea temperatures on the Cote d'Azur sit comfortably above 20 degrees for months, and a boat left on a berth or a swinging mooring fouls fast in warm, still, nutrient-rich water. That tempts owners toward the strongest copper paint they can buy, which is exactly the wrong instinct in the basins where biocide accumulates worst. The better Med answer is a copper-free or low-leach coating kept clean by regular in-water wiping, so you fight the growth with a sponge rather than ever-stronger poison.
The other variable is your hull. Steel and GRP tolerate copper; aluminium does not, because copper paint in contact with an aluminium hull drives galvanic corrosion. If you cruise an aluminium boat, copper-free is not a green preference, it is a structural requirement, and the cleaner choice happens to be the only safe one.
Application matters as much as the paint
The cleanest paint in the world becomes a pollution problem if you apply it badly. The single biggest avoidable harm from antifouling is the old stuff: dust from dry-sanding and chips from scraping, full of accumulated biocide, blowing across the yard and washing into the water.
French yards increasingly require you to contain it, and the responsible way is the only way: tarp under the hull, vacuum sander rather than open dry-sanding, dust bagged and put in the hazardous-waste skip, not swept onto the ground. Wet-sanding contains the dust but produces a toxic slurry, so it needs collecting too. Never tip leftover paint, thinners or roller-washings down a drain or over the side; the yard will have a dedicated point for them.
Whatever you put on the hull, where you then anchor it matters too. A copper-leaching hull parked over a seagrass meadow does double harm, so the cleaner-paint decision goes hand in hand with the wider rules on the Mediterranean coast that I set out in my guide to the Posidonia anchoring ban in France.
What I actually do
I run a copper-free hard antifouling now. It cost noticeably more than the cheap copper tin I used to buy, and I had to strip back years of old copper paint first, which was a filthy weekend. But it suits my aluminium-friendly conscience, it lasts, and I have stopped feeling like a hypocrite anchoring over a seagrass meadow with a hull painted in something that poisons it.
If you are not ready for that jump, the next best thing is honest discipline: the lowest-copper paint that does the job for your waters, applied cleanly, sanded into a tarp, with the waste taken to the proper skip. The choice of tin matters. What you do with the old paint matters just as much, and that part is free.
