• TotalBoat Underdog Boat Bottom Paint Black Gallon
  • TotalBoat Underdog Bottom Paint: Copper Biocide for Economical Protection
  • TotalBoat Underdog Bottom Paint: Free Paint Suit & Supplies Included with Gallon Purchase
  • TotalBoat Underdog Bottom Paint: Trusted by DIY Boaters & Marine Pros
  • TotalBoat Underdog Bottom Paint: Ablative Formula for Consistent Biocide Release
  • TotalBoat Underdog Bottom Paint: Easy Application for Professional Results
  • TotalBoat Underdog Bottom Paint: Paint Now, Launch Later
  • TotalBoat Underdog Bottom Paint: Available in 3 Popular Colors
  • TotalBoat Underdog Bottom Paint: Prime Bare Surfaces with TotalProtect for Maximum Adhesion
  • TotalBoat Underdog Bottom Paint Color Chart
  • TotalBoat Underdog Bottom Paint Black
  • TotalBoat Underdog Bottom Paint Blue
  • TotalBoat Underdog Bottom Paint Red
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GREAT FOR TRAILERED BOATS

Durable finish withstands abrasion from beaching & trailering
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SINGLE-SEASON ABLATIVE PROTECTION

Apply on fiberglass, wood & steel hulls in salt or fresh water
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COPPER BIOCIDE FORMULA

23.7% cuprous oxide load prevents hard and soft growth in low fouling
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BONUS SUPPLIES WITH GALLONS

Free paint suit, roller, tray, and prep tools with gallon orders

Underdog Boat Bottom Paint

Underdog Boat Bottom Paint

SKU: 365268
For seasonal boaters in low to moderate fouling conditions who need reliable, economical protection, Underdog delivers. Its 23.7% copper ablative formula keeps barnacles, slime, algae, and grasses off fiberglass, wood, and prepared steel or iron hulls in fresh or salt water, while wearing away gradually to expose fresh biocide and reduce paint buildup between seasons. The finish is tougher than most ablatives, which makes it a great choice for boats that get trailered or beached regularly.
$139.99
Color: Black
$139.99
$139.99
Free Shipping On All Orders
Security Icon

GREAT FOR TRAILERED BOATS

Durable finish withstands abrasion from beaching & trailering
Security Icon

SINGLE-SEASON ABLATIVE PROTECTION

Apply on fiberglass, wood & steel hulls in salt or fresh water
Security Icon

COPPER BIOCIDE FORMULA

23.7% cuprous oxide load prevents hard and soft growth in low fouling
Security Icon

BONUS SUPPLIES WITH GALLONS

Free paint suit, roller, tray, and prep tools with gallon orders
View full details
Description

DURABLE SINGLE-SEASON ABLATIVE BOTTOM PAINT

TotalBoat Underdog is an economical antifouling coating for recreational boats. It's tough finish makes Underdog ideal for boats that are trailered or beached regularly throughout the season. 23.7% Copper biocide helps prevent barnacles, slime, algae, and weeds on fiberglass, wood, and primed steel hulls below the waterline in freshwater, saltwater, and brackish waters.

Unlike softer traditional ablative paints, Underdog dries to a tougher finish that better withstands abrasion from hauling or relaunching while still gradually wearing away underway to continuously expose fresh biocide for reliable antifouling protection. Perfect for powerboats and sailboats in light-to-moderate fouling conditions, especially boats used seasonally or stored out of the water between trips.

EASY TO APPLY - EVEN OVER OLD BOTTOM PAINT

Underdog applies smoothly on properly prepared fiberglass, wood, and primed steel hulls using a brush, roller, or spray equipment. A 3/16" nap solvent-safe roller provides even coverage across larger surfaces, while foam or chip brushes work well around waterlines, chines, strakes, and fittings. For larger hulls and commercial applications, Underdog can also be applied using conventional or airless spray equipment.

Depending on application conditions and equipment setup, this bottom paint can be thinned up to 10% using TotalBoat Brushing Thinner 100 or Spray Thinner 101. Ablative formula reduces heavy paint buildup for easier maintenance

Not sure how much boat bottom paint you’ll need? Try our bottom paint coverage calculator to estimate how much you'll need for your project.

FLEXIBLE HAUL AND RELAUNCH SCHEDULES

Underdog dries quickly with no sanding required between coats under normal recoat conditions, helping simplify seasonal bottom painting projects. Depending on temperature and humidity, the coating dries to recoat in as little as 1.5 hours. For best results, apply between 50-90°F with humidity below 90%.

Need flexibility around launch timing? Underdog features no maximum dry time before launch, allowing you to prep and paint ahead of schedule without losing antifouling effectiveness. If your boat sits out of the water for more than 2 weeks, reactivate the biocide with a light scuff-sand before splashing.

UNDERDOG ANTIFOULING PAINT FOR TRAILERED BOATS

  • Durable ablative antifouling paint perfect for recreational boats that are trailered, beached, or hauled regularly
  • Formulated with 23.7% cuprous oxide to help prevent barnacles, slime, algae, and weeds
  • Tougher cured finish withstands trailering and beaching better than many traditional ablative paints
  • Wears away gradually underway to continuously expose fresh biocide with less paint buildup over time
  • Works on fiberglass, wood, and primed steel hulls below the waterline in saltwater, freshwater, and brackish water
  • Compatible with most existing hard and ablative antifouling paints in good condition
  • Apply by brush, roller, or spray; thin up to 10% with TotalBoat Brushing Thinner 100 or Spray Thinner 101 if needed
  • No sanding required between coats under normal recoat conditions
  • No maximum dry time before launch for flexible spring prep and maintenance schedules
  • Colors: Choose from Black, Blue, and Red
  • Sizes: Available in Gallons
  • Gallon Bonus: Each Gallon order includes a paint roller frame, recommended 3/16″ nap solvent-safe roller cover, metal tray, 10" stir stick, XL paint suit, 2" chip brush, a maroon abrasive pad, and a roll of 1" painter’s tape. For additional supplies, we also offer this Bottom Painting Supplies Kit separately.
  • Recommended Primer: TotalBoat TotalProtect Epoxy Barrier Coat Primer
  • Recommended Brush: Chip Brushes
  • Not for use on aluminum hulls - use TotalBoat AlumiPaint AF Aluminum Antifouling Paint or TotalBoat Krypton Copper-Free Bottom Paint on aluminum
  • Storage: Store in a cool, dry, well-ventilated area, protect from freezing.

FREQUENTLY BOUGHT TOGETHER

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PRODUCT IN ACTION

SEE HOW EASY IT IS TO USE TOTALBOAT ANTIFOULING PAINT

PRODUCT IN ACTION

SEE HOW EASY IT IS TO USE TOTALBOAT ANTIFOULING PAINT

SPECIFICATIONS

TECHNICAL DATA

APPLICATION DATA
  • Substrates: Properly prepared wood, fiberglass, steel, iron, and previously painted substrates. Not for use on aluminum hulls. For aluminum and underwater metals, see TotalBoat Krypton copper-free bottom paint, TotalBoat AlumiPaint AF, and TotalBoat Outdrive AF.
  • Application Method: Brush (chip brush), Roll (3/16" solvent-safe nap or foam roller cover), Spray (conventional or airless)
  • Number of Coats: 2
  • Film Thickness (per Coat): 1.5 mils dry (3.5 mils wet)
  • Coverage: 500 square feet per gallon
  • Application Conditions: 40-90ºF, relative humidity 0-90%
  • Dry Time to Overcoat: 1.5 hours @ 90ºF, 3 hours @ 70ºF, 6 hours @ 50ºF
  • Dry Time to Launch: 6 hours @ 90ºF, 10 hours @ 70ºF, 16 hours @ 50ºF
  • Colors: Black, Blue, Red
  • Size: Gallon
PHYSICAL DATA
  • Applicable Waters: Brackish, fresh, and salt water
  • Base: Solvent-based
  • Finish: Flat
  • Seasonal Protection: Single
  • Applicable Waters: Salt water & fresh water
  • Storage: Keep from freezing
  • Biocide: 23.70% Cuprous Oxide
  • Launch Window: There is no maximum dry time before launching.
PRIMER, THINNER, PREP & CLEANUP SOLVENTS
  • Primer: TotalBoat TotalProtect Epoxy Barrier Coat Primer
  • Thinner - Brush/Roll: TotalBoat Brushing Thinner 100, TotalBoat Spray Thinner 101 (Cool weather below 60°F)
  • Thinner - Spray: TotalBoat Spray Thinner 101
  • Surface Prep Solvent: TotalBoat Dewaxer & Surface Prep or TotalBoat Special Brushing Thinner 100 or TotalBoat Spray Thinner 101
  • Cleanup Solvent: TotalBoat Dewaxer & Surface Prep or TotalBoat Special Brushing Thinner 100 or TotalBoat Spray Thinner 101
HOW IT COMPARES
  • TotalBoat Underdog Boat Bottom Paint Black Gallon

    Underdog Boat Bottom Paint

  • Use for:
  • Seasonal Protection:
  • Colors:
  • Base Formula:
  • Applicable Waters:
  • Biocide:
  • Substrates:
  • Primer:
  • Coverage:
  • Recoat Time:
  • Minimum Dry Time to Launch:
  • No Max Dry Time to Launch:
  • THIS ITEM
  • TotalBoat Underdog Boat Bottom Paint Black Gallon

    Underdog Boat Bottom Paint

  • Use for: Trailered boats and shorter boating seasons
  • Seasonal Protection: Single season
  • Colors: Black, Blue, Red
  • Base Formula: Solvent-based
  • Applicable Waters: Salt water & fresh water
  • Biocide: Cuprous Oxide - 23.70%
  • Substrates: Fiberglass, wood, steel, iron, and properly prepared previously painted substrates
  • Primer: TotalBoat TotalProtect Epoxy Barrier Coat Primer
  • Coverage: 500 sq ft/gal
  • Recoat Time: 1.5-6 hours
  • Minimum Dry Time to Launch: 6-16 hours
  • No Max Dry Time to Launch: ✓
  • TotalBoat JD Select Black Gallon

    JD Select Water-Based Boat Bottom Paint

  • Smooth DIY application and easy cleanup
  • Single season
  • Black, Blue, Red, Green
  • Water-based
  • Salt water & fresh water
  • Cuprous Oxide - 25.25%
  • Fiberglass, wood, steel, iron, previously painted surfaces in good condition (do not apply over tin, vinyl or Teflon)
  • TotalBoat TotalProtect Epoxy Barrier Coat Primer (Fiberglass, Steel, Iron)
  • 500 sq ft/gal, 125 sq ft/qt
  • 1.5-6 hours
  • 6-16 hours
  • ✓
  • TotalBoat Spartan Blue Gallon

    Spartan Multi-Season Boat Bottom Paint

  • High copper protection and less painting
  • Multi-season - apply at least one coat of Spartan per season of protection.
  • Black, Blue, Green, Red
  • Solvent-based
  • Salt water & fresh water
  • Cuprous Oxide - 37.50%
  • Fiberglass, wood, steel, iron, and properly prepared previously painted substrates
  • TotalBoat TotalProtect
  • 500 sq ft/gal, 125 sq ft/qt
  • 2-6 hours
  • 2-8 hours
  • ✓
  • TotalBoat Krypton Copper-Free Antifouling Bottom Paint

    Krypton Copper-Free Boat Bottom Paint

  • Copper-free compliance and brighter colors
  • Single season
  • Black, Blue, Green, Red, White
  • Solvent-based
  • Salt water & fresh water
  • Zinc Pyrithione: 4.80% and Tralopyril: 6.00%
  • Fiberglass, wood, steel, iron, aluminum, and properly prepared previously painted substrates
  • TotalBoat TotalProtect or TotalBoat Aluminum Boat Barrier Coat
  • 500 sq ft/gal, 125 sq ft/qt
  • 1-4 hours
  • 2-8 hours
  • ✓

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WHAT MOST PEOPLE ASK

FREQUENTLY ASKED QUESTIONS

  • What types of boats can this antifouling paint be used on?

    Underdog can be used on fiberglass, wood, primed steel and previously painted surfaces in good conditions. This durable bottom paint is a great choice for trailered or beached boats, fishing boats, sailboats, powerboats, and other recreational boats in light-to-moderate fouling conditions.

  • Can I use this paint on aluminum boats?

    No. Underdog contains 23.7% cuprous oxide (copper), and should not be used on aluminum boats due to the risk of galvanic corrosion. For aluminum and underwater metals, see TotalBoat Krypton copper-free bottom paint, TotalBoat AlumiPaint AF aluminum bottom paint, and TotalBoat Outdrive AF spray.

  • Is Underdog safe for all waters?

    Underdog can be used in salt, fresh, and brackish waters with light-to-moderate fouling conditions.

  • Does it require a primer?

    Underdog can be applied directly over existing paint. On bare fiberglass, gelcoat, wood, steel, and iron, it is strongly recommended to prime first with TotalProtect Epoxy Barrier Coat Primer to help prevent water absorption and improve adhesion.

  • Can I apply Underdog over old paint?

    If the hull has been previously painted and is in good conditon, Underdog can be applied directly over after preparation. Reference our Antifouling Compatibility Chart for what works and how to best prep before painting.

  • How should this bottom paint be applied?

    Apply 2 coats of Underdog with a 3/16" nap roller, foam and chip brushes, or airless and convention sprayers. An extra 1-2 coats are recommended over bare substrates, at the waterline, and other areas with increased wear, such as leading edges of rudders, skegs, or struts. If needed, thin up to 10% (12 oz. per gallon) with Brushing Thinner 100 (brush/roll application) or up to 5% with Spray Thinner 101 (sprayer application).

  • How much antifouling paint do I need?

    Explore our boat bottom paint calculator to help you estimate how much Underdog you'll need for your project. One gallon typically covers 500 square feet.

  • How long does Underdog take to dry?

    Depending on the temperature, Underdog dries and is ready to overcoat at 1.5 hours (90ºF), 3 hours (70º), or 6 hours (50ºF).

  • How long after applying can I launch my boat?

    For best results, allow the paint to cure overnight before launching. Dry time to launch is 6 hours @ 90ºF, 10 hours @ 70ºF, and 16 hours @ 50ºF. There is no max dry time to launch, as the copper biocide remains active until the boat hits the water.

  • Can I apply Underdog above the waterline?

    Antifouling paint is to be used below the waterline only. It is not a general purpose marine paint. does not contain UV resistance, and is an ablative finish designed to wear away with use, constantly exposing fresh biocide.

  • What can I do to maximize antifouling performance?

    We recommend that the bottom of the boat be checked regularly to make sure it is clean and that no growth is accumulating. The self-cleaning nature of this coating is most effective when the boat is used periodically.
WARNING: This product contains a chemical known to State of California to cause cancer, birth defects, or other reproductive harm. For more information, go to www.P65Warnings.ca.gov