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How to Keep A Clean Boat Bottom

By The Ahoy! Crew
Published July 27, 2022

Has your formerly-sleek boat hull transformed into a reef? Do you find your boat less receptive to steering or moving slowly through the water? Have fish started hanging out around the bottom of your boat? Then it’s time to stop putting off hull cleaning. Hiring hull cleaning divers is always an option, but with the right tools and a little bit of time and energy, everyday boat owners can tackle this task by themselves—without hauling the boat out of the water. Read ahead to learn how to properly clean the hull of your vessel and what to consider before undertaking this overhyped boat chore. 

What’s going on down there?

There are three principal groups of fouling species that can be found in most bodies of water on our planet: animals, weeds, and slime. Animals like hard-shelled mussels or mollusks are typically the most difficult to remove, while slime and weeds may come off with a sponge or microfiber towel. Slime typically appears first, spreading quickly and promoting the establishment of other fouling species. The specific fouling species will depend upon your marine environment, so it’s important to consider when evaluating how regularly you should attack this marine growth.

Antifouling Paints—What do you have below the waterline?

Your cleaning your boat bottom strategy depends on the type of antifouling paint found below the water. Hard antifouling paint dries solid and strong, with only minor reductions in the top paint layer due to abrasive material in the water. Ablative “soft” paint is designed to slowly erode, bleeding into the water and thus carrying away any kind of organism that may attempt to stick to the surface. Both of these paints work by releasing “biocide,” a chemical agent that destroys living organisms. Hard antifouling paint can withstand scrapers and more abrasive brushes without affecting the lifetime drastically, whereas ablative paint requires more care and precision when cleaning to preserve its effectiveness. Remember which paint you have below the surface when considering the right tools for your cleaning job.

There’s nothing like having the right tools to get a job done

Winston Churchill once said, “Give us the tools, and we will finish the job.” Equipping yourself with the proper tools to handle your hull cleaning will ensure effectiveness and high productivity, reducing the amount of time you spend working on this chore. To start off, select a comfortable pair of gloves to wear in the water since barnacles can be sharp and cut the skin. Then, assess the equipment you will use while in the water. Access to a scuba tank and scuba gear makes cleaning your hull easier since it eliminates the need to constantly resurface for air.

Those using scuba gear should also use a weighted belt to conserve energy since it will keep them from floating to the surface. Those without a weighted belt can opt for other options, such as a plunger, which can be stuck onto the boat below the water’s surface. No worries if you don’t have scuba gear though—snorkeling gear - a mask, a snorkel, and fins - will work just fine. 

As for the actual cleaning, there are many options, ranging from costly electric rotary brush systems to standard microfiber towels. Most people will simply need a hard scraper for the more heavy-duty animal removal, a scrubbing pad, a sponge, a brush, and a long, skinny tool of choice for clearing out thru-hull fittings, which can sometimes become home to marine growth.

Only use the heavy-duty scraper when necessary, and always start with the least-abrasive cleaning material before working your way up. The less abrasive your cleaning tools, the longer your bottom job and antifouling paint will last.  

The C-Pole is a new innovation for people living in colder environments or who simply do not want to enter the water to clean their vessel. A C-Pole is a 3-meter/9-foot rounded pole (hence “c,” due to its C shape) that lets boat owners clean the bottom of their boat from the comfort of the deck. The C-Pole even has different heads depending on your needs, ranging from microfiber pad to scrubbing pad to soft brush. 

Remember: fiberglass boats should be cleaned with caution since some of the more abrasive materials could open up bigger problems if they puncture a blister or weak spot in your boat. Instead, stick to the sponges and microfiber towels when handling fiberglass. 

Bonus checklist: Tips and Things to Consider Before Cleaning Your Hull
  • Buddy system: Make sure someone knows you’re going in the water to clean, and have them nearby in the dinghy, watching should an emergency arise.
  • How will you get out of the water after the job is complete? (Plan this BEFORE entering the water; if your boat has a swim ladder, this will be simple. If not, you’ll have to be creative)
  • Address critical areas of your vessel first. For example, the propeller, the rudder, and running gear, since these are most impacted by marine growth buildup
  • Check the forecast and make sure the weather is favorable
  • Be aware of your surroundings (avoid entering the water if there is regular boat traffic) and put up your diver down flag/scuba flag, if possible
  • Clean the areas at and around the waterline from your dinghy. This will drastically reduce the time you have to spend in the water
Maintenance, maintenance, maintenance!

The most effective way to avoid a full day of grueling and exhausting boat cleaning is to stay on top of the marine growth with regular hull scrub downs. If done properly, you can clean the bottom of your boat in an hour or so. If you add hull cleaning to your weekly or biweekly chore list, then you won’t just have a clean bottom: you’ll have increased speed, a better performing motor, and all-around improved boat performance. And don’t forget: a well-maintained vessel will treat you well in return. 


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