Bottom Paint 101: All About Anti-Fouling Paint from TotalBoat

Ah, bottom paint season—when boatyards come alive with sanding, scraping, and painting as everyone gets their boats ready for splash. If you're one of the many boaters wondering, “Which bottom paint is right for my boat?”—you're not alone. We're getting tons of questions, so we put together this handy guide to walk you through the basics and break down the different types of TotalBoat bottom paint we offer.

So whether you’re a first-timer or a seasoned pro looking to try something new, this blog is for you!

Let’s dive in (but, you know… figuratively).

Cover & Header Image: Spartan in Green

What Does Bottom Paint Actually Do?

Bottom paint (also known as antifouling paint) helps protect your boat’s hull from marine growth like barnacles, algae, slime, and zebra mussels. This build-up doesn’t just look gnarly—it can drag down your speed, fuel efficiency, and overall performance.

Bottom paint is a must-have line of defense if your boat spends any time in the water (as it should), especially in saltwater or warm climates.

How It Works: Biocides + Paint Film

Bottom paint is made with biocides (like copper or other metal-free alternatives) that deter marine growth. These biocides are suspended in a paint film that slowly releases them over time.

Two main types of paint films:

Ablative: Wears away slowly, exposing fresh biocide as it erodes. Think of it like a bar of soap.
Hard (Modified Epoxy): Forms a tough, smooth surface. Great for high-speed or frequently trailered boats. Less erosion = less maintenance.

Choosing the Right Type: Ablative vs. Hard Paint

Ablative paints are great for:

Boats that move often
Seasonal boaters
Anyone wanting an easy maintenance routine (minimal buildup year over year)

Hard paints are ideal for:

High-speed boats
Trailered boats (paint won't rub off on bunks)
Boats that stay in the water long-term

Don’t Forget the Primer

Before you break out the bottom paint, make sure you’ve considered whether a primer is needed. Primers help create a strong bond between your hull and the bottom paint, and in some cases, they’re essential—especially on bare fiberglass, aluminum, or when switching paint types.

Here are the two main TotalBoat primers made specifically for bottom painting:

🛡️ TotalProtect Epoxy Barrier Coat Primer

Best for: Fiberglass, steel, and wood
Use it when: You need a moisture barrier on bare fiberglass, you're switching incompatible bottom paints, or you want added protection from water intrusion (osmosis).
Bonus: Also works great under topside paints for complete below-the-waterline defense.

Learn more about TotalProtect

⚙️ Aluminum Boat Barrier Coat Epoxy Primer

Best for: Aluminum and galvanized metal boats
Use it when: You’re applying antifouling paint to bare or prepped aluminum. This primer prevents corrosion and ensures excellent paint adhesion.
Bonus: Compatible with copper-free antifouling paints like AlumiPaint AF.

Learn more about Aluminum Boat Barrier Coat

The TotalBoat Lineup: Which Paint Is Right for You?

Here's a closer look at each of our antifouling paints:

⚓ JD Select – Water-Based Ablative

Best for: Boats in freshwater or low-fouling saltwater
Why people love it: Soap-and-water cleanup, low VOCs, and great performance for the price
Pro tip: Excellent choice for DIYers working indoors or in well-ventilated garages

🛥️ Spartan – High-Copper Ablative

Best for: High-fouling saltwater environments
Copper content: 45–65%
Why people love it: Long-lasting protection, excellent for both power and sailboats
Pro tip: Apply two coats, and you’ll be set for serious saltwater season

🚤 Krypton – Copper-Free Ablative

Best for: Boats in copper-restricted waters
Why people love it: Dual-biocide formula offers strong protection without metal restrictions
Pro tip: Ideal for boaters navigating sensitive or eco-regulated zones

🐚 Underdog – Affordable Ablative

Best for: Seasonal boaters or boats in low to moderate fouling areas
Why people love it: Easy to use, solid protection at a budget-friendly price
Pro tip: Great for older hulls where premium performance isn't essential

🔧 AlumiPaint AF – Copper-Free for Aluminum

Best for: Pontoon boats, aluminum hulls, and underwater metals
Why people love it: Will not cause galvanic corrosion, applies easily
Pro tip: Don’t forget to prep with Aluminum Boat Etch Wash to ensure adhesion on bare aluminum

🌊 Outdrive AF – For Running Gear & Metals

Best for: Outdrives, trim tabs, lower units, and underwater metals
Why people love it: Copper-free and safe for use on all underwater metals
Pro tip: Ideal for applying over zinc chromate-primed outdrives

Above: Krypton in Red

Surface Prep Tips Before You Paint

Clean the hull: Remove old paint if it's flaking or incompatible with your new paint.
Sand or scuff: Ensure proper adhesion by roughing up the surface.
Use a primer/barrier coat when necessary: This is especially important if you're painting bare fiberglass, switching paint types, or preventing water intrusion.

Want a smooth job that sticks? Don’t skip the prep! Our tech data sheets (available on each product page) contain helpful information on surface preparation and application.

Your Bottom Paint Questions—Answered!

Q: Can I use bottom paint on my trailer boat?
A: Yes! But a hard paint is a better choice than an ablative, which can wear off from trailering.

Q: How long does bottom paint last?
A: Depends on use, water conditions, and the product. Spartan and Krypton last multiple seasons; Underdog and JD Select are better suited to single-season use.

Q: Do I need to paint every year?
A: If your paint shows signs of wear, yes. But if you haul your boat early and your bottom paint still looks solid, you may get more than one season out of it—especially with high-copper formulas.

Q: What’s the best bottom paint for aluminum boats?
A: AlumiPaint AF is your go-to—it’s copper-free, won’t corrode metal, and is designed for aluminum hulls and pontoons.

Q: Can I apply this myself?
A: Definitely! Most TotalBoat bottom paints are designed for DIYers and can be applied by brush, roller, or spray.

Still from our Waterlust Ambassadors, 'How to Paint a Trailer Sailer' Youtube Video using JD Select in Red

See Spartan (Blue) in action with Sailing Catalpa on YouTube

Ready to Paint?

Once you've chosen your paint and prepped your surface, you're ready to go. Apply two good coats and let them dry according to the instructions on the label. Don't forget to tape off your waterline, wear proper protection, and stir that can well before applying.

Still unsure? Reach out to our tech support team—we’re happy to help.

Helpful articles to check out:

Bottom Paint Commonly Asked Questions

Primer Commonly Asked Questions

Bottom Paint 101: The Basics of Bottom Paint

And if you are a visual learner, make sure to check out our Bottom Painting Playlist on YouTube

Whether you're gearing up for a big launch or just trying to keep your hull clean and efficient, the right bottom paint makes all the difference. Save this blog as your go-to resource this spring and let TotalBoat help you stay one step ahead of marine growth.