Barnacles On Your Boat: What You Need To Know

When you leave a boat in seawater for even just a month, barnacles can begin to grow on your hull. If you leave your boat in all season, the hull could be covered in barnacles such as in the image above. So, before I get into how to prevent them, let’s talk about what barnacles even are:

Barnacles are arthropods and are considered in the crustacean family, meaning they are relatives to crabs, lobsters, and shrimp. Barnacles love sticking to places with lots of activity, making boat hulls a primary target. Due to how strong their natural glue is, getting them off is not easy.


Barnacles are most common on boats left in saltwater all season long. Those who have boat lifts or store their boat out of the water won’t have to worry about barnacle growth on their hulls. However, barnacles may grow on the parts of docks and lifts that are below the water level. They are attracted to any hard surface that’s easy to stick to.

How do barnacles affect boats?

The primary effects of barnacles on your boat are increased drag and increased corrosion due to paint loss. Increased drag and increased weight from barnacles attached to a hull slow the boat down and make the boat less fuel-efficient. Also, barnacles can break up your paint and cause the metal beneath the paint to start rusting.

Many times barnacles are so strongly attached to your hull that in order to get them off, you will also have to take off your paint. This will cause you to put a new layer of bottom paint on your boat.

Including increased drag and corrosion, there are many other issues barnacles cause to your boat. Below I explain each and every one of them in full detail:

Increased drag

The more barnacles that connect to your hull, the more drag your boat will have against water. This can lead to a variety of problems, including:

  • Reduced speed
  • Reduced fuel efficiency
  • And reduced engine lifespan

A boat that is fully covered in barnacles will experience a speed reduction of up to 60% of its original speed. And to reach cruising speed, it will require much more RPMs out of the engine, meaning more fuel will be used, and the engine will age quicker.

The U.S. Naval Academy estimates that biofouling creates enough hull-drag to increase the Navy’s petroleum bill by about $250 million every year.


Biofouling describes barnacles and other marine organism growth on marine vessels.

Damage hull surfaces

Barnacles can cause gel coat and paint damage when you clean them off. The longer you let the barnacles grow, the more damage they will cause when you clean them off. Sometimes you may even have to repaint your bottom paint if it’s too bad.

Some damages that barnacles can cause include:

  • Calcium stains
  • Paint damage
  • And corrosion due to rust

Many boats that spend their life in seawater are anti-fouled at least once a year to avoid these damages. This includes power washing and painting the hulls with anti-foul paint. Many people even recommend cleaning the hull once every 3 months as well.

Cleaning the hull includes either taking it out of the water and power-washing/scrubbing or underwater scrubbing. You may have to learn how to scuba dive in order to clean everything or pay a scuba cleaner to do it for you.

Corrosion damage rarely occurs, but if you leave barnacles on your boat for too long, they may eat away your paint. No paint means that the steel will be in danger of corroding because it is exposed directly to seawater.

Clog water intakes

If barnacles grow over your impeller or get into your impeller, it could cause a reduction in water flow through your engine. A reduction of water flow through an engine can cause:

  • Engine overheating
  • Reduced engine lifespan
  • And possibly engine failure

So if you have an outboard motor, always raise it out of the water when you’re not using it. Inboard engines need to be scrubbed or power washed around the impeller at least once every 3 months (especially if your antifouling paint is wearing off).

Disrupt propellers movement

Propellers are designed in a way that any imperfections will cause them to be less effective. If you don’t clean your propeller often, barnacles will start to make them imperfect and disrupt their movement. This will cause your boat to:

  • Be less fuel-efficient
  • And be slower

So many people use propeller antifouling paint and clean their props once every 3 months to help avoid any barnacle growth.

Cover transducers

if barnacles were to grow on transducers or other instruments under the waterline, it could throw off or block their readings. You’ll need to use a hull cleaner such as this one and a plastic scraper in order to get barnacles off.

Harm the appearance of your boat

Barnacle growth not only harms your boat in many different ways, but it’s also ugly. It may be difficult to see barnacles when your boat is just floating. But when you start driving, the barnacle-covered hull will be visible.

How to get rid of barnacles on boats?

When it comes to getting rid of barnacles on your boat, there are 3 different things that you can do. These are:

  • Scrubbing them off
  • Power washing them off
  • And boating in freshwater

Generally, it’s easier to powerwash barnacles off of your boat because you can get a lot done in a short amount of time. However, when you powerwash barnacles off, you’ll usually have to scrub your hull again with hull cleaner to get any stains left by barnacles off.

And if you can’t get your boat out of the water, you’ll need to scrub the hull underwater. This generally requires you to dive under the boat with a scuba setup and scrub the boat. There are people you can hire to do this for you (especially in big cities) but expect to pay $2.5-$5 per foot.

And if you can, boating in freshwater will kill off any barnacles on your boat.

How to clean barnacles off of your boat while it’s out of the water

The easiest way to get barnacles off of your boat is power washing them off. You can do this yourself or hire a professional to do it for around $2-$3 per foot. However, if the barnacle growth isn’t that bad, sometimes just scrubbing it with a hull cleaner will be the better option.

The video below shows how power washing barnacles off is done:

Many times you’ll end up needing to use hull cleaner as well as power-washing anyways because there will still be stains left on your boat. So, if your barnacle growth isn’t that bad, just use a hull cleaner such as this one.

In order to clean off barnacles and barnacle stains with hull cleaner, all you need to do is brush off the hull with a medium-stiff brush and the hull cleaner. The stuff works like magic.

How to clean barnacles off of your boat while it’s in the water

Cleaning barnacles off your boat without taking the boat out of the water is much more difficult. You’ll need to find a way to get to the barnacles, and if your boat is big, you’ll have to go diving. However, you can try to use this barnacle scrubber that allows you to get under the boat without you having to get in the water.

If you need to dive to clean barnacles off your boat, check out the video below:

It’s recommended to do this once every 3 months. If you wait longer than that, the barnacles may become too stuck to get them off with a regular brush, and you’ll need to take your boat out of the water.

How to prevent barnacle growth on boats?

When you don’t have to deal with barnacles, you’ll become a happier person. Luckily, there are plenty of things you can do to prevent them. These include:

  • Spraying your hull with an anti-fouling coating
  • Painting your hull with anti-fouling paint
  • And cleaning off barnacle growth as soon as you spot it

Note: It’s best to avoid using anti-fouling products if possible because of its effects on water pollution and aquatic life. However, if you don’t use anti-fouling products, you’ll need to clean your hull off at least once every 3 months.

Anti-fouling clear coat

Anti-fouling coating such as this one on Amazon works great to protect any area of your boat that’s below the waterline from barnacles. Apply 2 coats once a year, and you’ll be set for the season. The good thing about this stuff is that it’s clear, so you don’t have to make your hull look ugly colored with anti-fouling paint.

Anti-fouling paint

If you want something longer-lasting and more durable, anti-fouling bottom paint such as this one on Amazon works great to prevent barnacles. It’s still recommended to repaint your bottom paint once every year to keep barnacles and any other marine growth off of your boat, but this stuff will be more durable than any clear coat.

Cleaning off barnacle growth

The longer you let barnacles stick to your boat, the more damage they will cause when scrapping them off. So to avoid this, not only do you want to use anti-fouling products, but you also need to scrub your boat the moment you see any marine growth.

As I’ve mentioned above, this may require you to get into the water to scrub the hull. Or you can try to use this barnacle scrubber that has a long handle for getting under your boat.

Frequently asked questions about barnacles on boats

How quickly do barnacles grow on a boat?

Barnacles can grow on boats as quickly as just a few days if you don’t have any anti-fouling products on your hull. So make sure to scrub your hull as often as possible, and never go longer than 3 months without at least inspecting your hull for barnacles.

How much does it cost to remove barnacles from a boat?

Depending on how much barnacle growth is on your boat, and if you hire a diver or a boat lift service to clean them, it’s going to cost anywhere between $2.5-$5 per foot.

Can I remove barnacles off my boat myself?

Yes, you can remove barnacles off of your boat yourself. However, you may need to take scuba diving courses to know how to dive under your boat.

How do barnacles stick onto boats?

Barnacles stick to boats by cleaning their surface and then excreting glue-like enzymes and fibrous tissues. This glue-like substance is so strong that scientists have studied barnacles to create an underwater super glue similar to the substance.

Does fresh water remove barnacles?

Yes, if you boat in fresh water after being in salt water, the fresh water will kill any barnacles on your boat and they will fall off. However, you will most likely still have calcium stains left from where the barnacles were. This can be cleaned by hull cleaner soaps.

Do you need to remove barnacles from boats?

Yes, you do need to remove barnacles from boats. If you don’t, the boat will be much slower, heavier, and less fuel-efficient. The engine will have to work up to twice as hard to push the boat, which could cause engine problems as well.