The 101 on Antifouling Paint

First, what is antifouling paint? It is a kind of paint used on boat hulls, more specifically, the part of the hull that sits below the waterline. Antifouling paint -commonly known as bottom paint- helps to prevents little subaquatic organisms from attaching to the hull of a boat while also decreasing their growth rate.

Why should you prevent these organisms from attaching to your boat's hull? Because they interfere with the overall function of the boat. When excessive growth occurs, they affect the performance, durability, speed, and fuel efficiency of your vessel.

What is the point of antifouling paint?

If your boat is stored on water or running for extended periods of time; slime, algae, barnacles, weeds, and the likes can attach to the hull and motor. As mentioned above, these organisms, once attached to your boat's hull prevents it from performing at its best.

At DS diving, we help to manage the levels of your antifouling paint through routine maintenance.

Ablative Paint vs. Hard Paint

While there are various forms of each, when it comes down to it there are 2 types of antifouling bottom paint: Ablative vs Hard. Choosing the right paint will depend on various aspects of how you use your boat and how it is stored.

Ablative paint

This paint is a soft bottom paint with a self-polishing attribute. Meaning it possess properties that allows the coating to wear off in layers, at a controlled rate. Oxidation occurs when out of water, then, when the boat re-enters the water the oxidized layer will wear off and allow a new layer to be exposed.

Ablative paint is a rather new product and bottom paint method. Even though its newer than hard paint it has fast become the favorite of many boaters, generally recreational boat owners. This is because it generally lasts longer than hard paint, allows for trailering or lift storage and there is continuously a new active coating unveiled to protect your hull.

Hard paint

Hard paint is a modified epoxy paint. It is known for its durability because it stays on for long time without wearing out, and it has a high amount of pesticide (no we aren’t talking about the kind that is gets a bad rep, we are taking about copper and other metals) properties that help disrupt and prevent marine growth.

This paint is normally used for anglers, boaters, and captains that wet store their boat or use their boat at-least every 2 days. This is because if you remove a boat from the water when there is ‘hard’ bottom paint covering the hull, within 72 hours (3 days) the paint becomes oxidized and therefore ineffective. Unlike ablative paint that allows for the oxidized layer to slip away, with hard paint, you would have to reapply a new layer of hard paint before putting your vessel back in the water, that is if you still wish to protect it from the elements.

Before deciding on your paint, ask yourself these questions:

There are several types of bottom paint; the kind you choose depends on various things like how you store your vessel, how often it is used, what type of factory paint was applies, etc.

Do you trailer, dry store or wet store your boat?

If your boat is stored in water, you trailer it or dry store it somewhere. When outside of water ‘hard’ antifouling paints oxidize and become less effective. Because of this, when stored on land or lift it is best to use an ablative paint.

Thanks to its soft and self-polishing properties, ablative paint takes time to wear out even when not on water. Using a copolymer paint that lasts considerably longer, is also a good choice. All you need to do is recoat from time to time for it to reactivate.

Is your boat hull made of aluminum?

Using bottom paint containing cuprous oxide can be corrosive and damaging if your boats hull is aluminum. So, you will want to choose an antifouling paint with non-metallic properties or zinc compounds.

Does your area have regulations against paint containing copper biocides?

If this is the case, you can use bottom paints that are metal free or made with zinc. Biocide free paints instead offer an extra smooth and glossy finish to prevent marine attachment, while biocide filled paints use the metal inclusions to deter marine growth.

Are the water bodies around you prone to algae and slime?

Irgarol is a bottom paint additive that enhances the photosynthesis of algae, helping to control its growth rate. Therefore, coating your hull with bottom paints that contains Irgarol additives will help prevent the growth of algae and slime.

What bottom paint was last used on your hull?

If you intend to change the type of bottom paint you used on your hull, it is recommended to stick with it (ex. If you used ablative paint before, continue using ablative paint, etc). You want to be sure not to coat an old soft bottom paint on your hull with hard bottom paint. This will make your bottom paint ineffective.

If you do still plan to switch paint types, you will need to sand or sandblast the previous paint. This will ensure that the new paint adheres to the hull and is effective. Additionally, if the old paint was vinyl-based, the new antifouling paint should possess the same properties.

Are you using your boat on saltwater or freshwater?

This is an important question to help you determine what paint to apply to your hull. Typically, there is less marine growth in freshwater vs saltwater. Because of this you can apply paint with less active ingredients like copper and zinc.

If you stick to the salty seawater be sure to choose either an ablative or hard paint that contains plenty of copper, zinc, or the like. Sea life, barnacles and slime are quicker to attach themselves to your hull when in saltwater.

How do you use your boat? Do you go fast or cruise? How often do you set sail?

If you use your boat frequently, whether for commercial or recreational purposes and it is stored in water, it is likely that you would want to use hard paint. Excessive use, with waves beating the hull, will erode ablative paint quicker, while hard paint will remain and continue to protect.

If you are a recreational boater that does not use their boat often or cruises rather than making waves, ablative paint may be the paint for your bottom. When a boat stay’s stationary or cruises along ablative paint will dissolve at a more controlled rate, lasting for a year or two. Hard paint can be used in this instance too and last just as long. However, it is a harsher coat and needs to be leveled and sanded before applying a new coat.

When to Repaint your Hull

No bottom paint lasts forever. Various elements, like how often you use your boat, how you store it and where you use it, will all determine how often you will need to reapply bottom paint. However, on average you should apply a new coat annually (preferably before the start of the season). This is not to say that some varieties of paint do not effectively last for two years.

If you believe you have one of the tougher paints that last 2 years, it is best practice to get your boat checked annually to evaluate the level and effectiveness of your bottom paint. This goes for both ablative and hard paints, alike.

Pro Tip: Routine hull cleaning and maintenance can extend the life of not only your bottom paint, but also your anodes, through-hull points, and running gear.

What does it take to Repaint Your Hull?

  • Ask yourself the above questions
  • Do the necessary research to find the right paint for your boat.
  • Take measurements to ensure you buy the proper amount of paint.
  • Remove flaky oxidized old paint & repair any gelcoat blisters.
  • Smoothen the hull (generally by sanding) and apply a primer basecoat.
  • Follow the standard safety precautions, like wearing a mask to protect from the fumes.
  • Buy your paint need and get started (be sure to follow the manufacturers recommended number of coats)

Skip the muss & fuss and let the professionals do it! Contact DS Diving for the name of local antifouling paint professionals.

Phone | (904)755-4546

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How to Maintain Your Bottom Paint

  • Properly prepare the hull before applying your antifouling paint, ensuring effectiveness.
  • Perform routine maintenance on your hull and running gear. This will aid in lengthening the lifespan of your bottom paint.
  • Try to prevent chips, dents, or cracks from happening.
  • Be sure your boat and slips electrical systems are grounded properly. Electrical currents in the water nearby or under your vessel can neutralize your bottom paint.


Protect the hull of your boat with antifouling paint. You can choose from a soft ablative paint of hard paint. Both paints last for a year or two. Ablative paint offers self-erosion elements; while hard paint must be properly sanded and primed before reapplication. How and where you use and store your boat will also play a role in the proper paint choice. Regular cleanings and maintenance can extend the life of your bottom paint.

If you trailer your boat, ablative paint is always the best option. This is because when hard painted boats are removed from the water, the paint oxidizes and becomes null within 72 hours with exposure to air. Ablative antifouling paint is also the top choice for recreational vessels due to the sporadic use of the vessel. If you use your vessel daily, hard paint will likely be your winner. The epoxy-based paint will stick to your hull and does not erode as easily as ablative paint.

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