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How to Clean a Boat Hull in the Water? – Detailed Guide

Written by Anthony Roberts / Fact checked by Jonathan Larson

how to clean a boat hull-in the water

Knowing how to clean a boat hull in the water is a crucial skill all boat owners must have to maintain their vessels in tip-top shape.

Professional boat bottom cleaning services can help, but cleaning the boat’s hull yourself is more cost-effective and strengthens the “bond” with your “baby.”

Most boats require an out-of-the-water cleaning to ensure more comprehensive “fouling” management. Such a task requires special equipment and tools, hiking the overall cost.

We prepared this guide to help you execute a fuss-free underwater hull cleaning without taking your boat out of the water. Check it out.

Ways to Clean Boat Hull in the Water


What to prepare for Underwater Boat Hull Cleaning


  • Putty knife, hull scrubber, and hull scraper (or a rotary brush system)
  • Wet suit, goggles, and snorkel (or scuba gear if certified)
  • Earplugs
  • Underwater work gloves

Step 1. Prepare for the activity.


Ensure to schedule the boat or ship hull cleaning in calm waters.

Plan where to position the hull cleaning equipment, tools, and materials so they’re all within your reach while still in the water.

Prepare an egress point for you to climb out of the water before removing barnacles from gelcoat. For instance, lowering and securing a ladder onto your boat’s side can make getting out of the water more convenient. If your watercraft has a swim platform, orient yourself to its location.

Unplug the boat from shore power to prevent electrical injuries. You might also want to turn off the vessel’s main power switch at the circuit breaker panel, just to be sure.

Don your scuba gear if you are certified. If not, a wet suit, flippers, snorkel, and goggles will suffice. You can also wear long sleeves as an alternative to wet suits to safeguard yourself against potential injuries related to removing barnacles on bottom of boat.

In any case, you should wear earplugs to keep dislodged marine organisms from entering your ears, although the chances of such things happening are relatively low.

Get into the water.

Step 2. Scrape barnacles and other organisms off the hull.


Boat owners must get barnacles off the boat’s hull to clean bottom of boat. They might also want to include other organisms, such as mussels, seashells, and other creatures accumulating on the hull’s surface.

Use a hull scraper and a putty knife to remove algae and detach other “fouling” organisms from the hull. When selecting scrapers, you should start with plastic ones to avoid damaging the hull, and only switch to more abrasive options when the barnacles are stubborn.

You can also use a rotary brush system, which is a good way to scrape barnacles off boat if you clean the hull more frequently, the vessel is too large, or the scum buildup is too stubborn.

Unfortunately, this cleaning machine is not cheap, so you might want to borrow from a friend if they have this device.

Step 3. Remove biofilm and slime, and clean the hull.



Completing the DIY boat hull cleaning involves brushing the surface to eliminate biofilm, slime, and other contaminants.

Among the hull scrubbers you can use to remove biofilm and slime, a boat sponge and soft brush are the best option. They’re both efficient without being so aggressive they’ll damage your vessel or the anti-fouling coating.

Whatever option you choose, be sure to scrub the hull in small sections for a better result. Should you encounter any stubborn grime or crevices, a putty knife will come in handy.

You can also use a citrus boat hull cleaner to remove grease and clean the hull without harming the environment. We also recommend boat hull cleaning pads and microfiber towels.

Some boaters use gravitational cleaning washers. It is like a pressure car washer, except you use this device to wash a boat hull underwater. Unfortunately, this system is costly and noisy.

Steps for Above Water Boat Hull Cleaning


This method is not as effective as cleaning boat hulls on dry land. Plus, please note this method requires upper body and arm strength, as the cleaning brushes’ extended poles make them quite heavy.

However, it remains a viable option, especially since the technique does not require extensive preparation. Moreover, it is better than not cleaning the hull ever.

What to prepare:

  • C-pole boat cleaner (or “Scrubbis” boat hull rotary brush)
  • Personal flotation device

Step 1. Prepare the tools


It is possible to clean the boat’s hull without getting your feet wet or diving into the water. You only need one of two things – a long-handled rotary brush or a C-pole boat cleaner.

You can think of either tool as a floor mop with a scrubber at the end. These cleaning materials only differ in the handle’s shape. The “Scrubbis” has a straight pole, while the C-pole is curved.

Alternatively, you can prepare a homemade rotary brush by connecting several PVC pipes together with a flat swivel-headed floor mop. To improve the DIY brush’s buoyancy, you can add floats to the swivel head’s upper side.

Step 2. Scrub the hull


Put on a personal flotation device in case you trip and fall into the water. Then, position yourself on the dock beside your boat and grab the scrubber’s long handle.

Extend the long-handled scrubber onto the boat’s hull starting at the waterline. Push the pole towards the keel and scrub in vertical motions.

Once you’re done cleaning one side of the vessel, get on the boat and position it in such a way that the uncleaned side is facing the dock. Then, proceed with your scrubbing.

Frequently Asked Questions


What is good for cleaning your vessel?

You have several options as boat cleaning tools. You can use a boat hull scraper, an extended rotary brush, a cleaning pad, and a C-pole boat cleaner.

You can also use a rotary brush system. However, this cleaning device requires the user to wear underwater gear to clean the bottom of a boat in the water.

A good rule of thumb to observe is to use environmentally friendly boat cleaning products, such as citric acid, to clean boat hulls and other components without polluting the water.

When to clean your boat hull?

You can clean the hull of your vessel every one to three months or when you notice “fouling” at the boat’s hull. “Fouling” occurs when barnacles, mussels, and similar marine organisms attach to the hull.

Boat hull cleaning frequency depends on vessel usage patterns, boat speed, geographical location, water salinity, regional variations, and water temperature.

For example, you might want to clean the boat’s hull more often if you rarely use your vessels, only take “slow” boat trips, or frequently travel in warm waters.

How much does it cost to clean a boat hull in the water?

Underwater boat hull cleaning prices vary according to vessel type and size.

For example, speedboats, jon boats, pontoons, and other small boats can have a base hull cleaning price of about $100 to $200.

Professionals might charge you a base price of $160 for cleaning the hull of your sailboat and a minimum of about $300 for yacht cleaning.

Meanwhile, some service providers charge per foot. For example, barnacle removal can cost you a dollar to five for every foot. Hence, if you have a 20-foot fiberglass boat, you can spend $20 to $100 to have the professionals remove barnacles for you.


You now know how to clean a boat hull in the water. And we hope you are confident in ensuring optimum boat performance and pristine condition by eliminating barnacles and other organisms from your boat’s hull.

You can either dive into the water and scrape organisms off the hull or keep your feet dry on the dock and scrub biofilm and barnacles with a long-handled tool.

Your third option is to hire a professional to clean your boat hull. It might be costly, but it gives you the result you want.

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