Seal-Once Marine Ready Mix - 2 Gallon Penetrating Wood Sealer Waterproofer & Stain (Clear). Water-Based, Ultra-Low VOC Formula for high-Moisture Areas to Protect Wood Docks, Decks & Piers.

Why I picked Seal-Once Marine for my dock and outdoor furniture

Coastal projects put finishes to the test. Between salt spray, fast-moving weather, and constant wet-dry cycles, I need something that protects without turning my deck into a slip hazard or gassing the shoreline with solvent fumes. I chose the Seal-Once Marine sealer because it’s water-based, ultra-low VOC, and rated safe for use over open water—exactly the profile I want for a dock landing and a small teak table I keep outdoors.

I used the clear version to keep the wood’s natural look. My goals were straightforward: stop water intrusion, avoid a plasticky film, and keep maintenance simple.

What it is

Seal-Once Marine is a penetrating, water-based sealer that forms a breathable, UV-stable, water-resistant barrier inside the wood fibers rather than a thick surface film. That matters for a few reasons:

• Breathable means it lets moisture vapor escape, reducing the risk of peeling and white blushing.
• Penetrating performance depends on clean, open pores; it’s far more sensitive to surface prep than heavy film finishes.
• Clear means it doesn’t dramatically alter tone—expect a mild “wetted” look on most species, without ambering.

It’s suitable for docks, decking, piers, outdoor furniture, and thermally modified wood. Being non-hazardous to aquatic life is a big plus for shoreline work.

Prep and test surfaces

This is not a “skip prep and hope” product. Penetration is everything.

• For my cedar dock landing, I cleaned with an oxygenated deck cleaner, let it dry thoroughly (I look for under 15% moisture on a meter), and sanded high-wear boards to 120–150 grit to open the grain.
• On the teak table, I stripped the weathered top, sanded through 150 and finished at 220. Teak’s natural oils can challenge some finishes, but this sealer took well on freshly sanded surfaces.
• I ran a quick penetration test: a light brush of product should disappear into the wood within a minute. If it sits on the surface and stays shiny, keep cleaning/sanding or reevaluate compatibility.

Avoid applying over previously oiled or waxy sealers. I spot-tested a scrap of old, oil-treated decking and the Marine sealer simply didn’t absorb well. In those cases, either strip thoroughly or stay with a compatible oil system.

Application experience

Application is where this product shines—if you keep coats thin and sequential.

• Tools: I had the best control with a 3/8-inch nap roller and a medium-stiff synthetic brush for back-brushing. A quality pump sprayer can work on verticals and railings; still plan to back-brush.
• Coats: The product is designed for two wet-on-wet coats. I applied the second about 15–20 minutes after the first—just as the first had absorbed and lost its sheen. If areas remained shiny, I wiped off excess before moving on.
• Coverage: Expect roughly 250–300 sq ft per gallon on smooth, sanded wood and less (150–200) on rough sawn. With two coats, the 2-gallon size comfortably handled a medium landing plus the table with some left over.
• Conditions: Low humidity and moderate temperatures help. I aim for the warmest, driest part of the day, avoiding late-afternoon applications that might meet evening dew.

Dry to the touch is quick—often under an hour—but I left the dock landing undisturbed for 48 hours. That conservative cure window pays off in durability and avoids any temporary tackiness.

Finish and appearance

This is a clear, low-sheen result with minimal color shift. On teak it revived the grain and deepened the tone slightly without producing a glossy, varnished look. On cedar decking, it tamped down fuzz from sanding and left a clean, natural finish that doesn’t feel plastic underfoot.

Importantly, it does not load the surface with a thick film. High-build, “wet look” fans will find it too understated; if you want a bright, glossy finish, this isn’t the right class of product.

Waterproofing and early durability

After the first full week of coastal weather—including a heavy squall—water beaded as expected and didn’t darken the grain. The breathable film helps avoid the trapped-moisture hazing you see with some film finishes when dew hits a not-yet-cured surface.

Salt spray is always the wild card. So far, there’s no whitish salt residue bonded to the finish, and rinsing the deck after storms has been straightforward. On high-traffic tread boards, I plan to clean and add a light maintenance coat every 2–3 seasons; shaded verticals should go longer.

UV resistance is solid for a clear sealer. You’ll still get gradual patina in full sun—no clear, breathable sealer permanently freezes color— but the wood has stayed even-toned without blotchy fade or yellowing.

Cleanup, odor, and safety

Low odor was immediately noticeable. Working above water without the solvent punch was a relief. Cleanup truly is soap-and-water simple; a little dish soap worked product out of brushes quickly. For sprayers, I always run warm water and then a mild soapy rinse to keep valves clean.

One practical note: the container arrived with a locking ring that was very secure. It takes a bit of persuasion with a flat screwdriver to remove, but I’d rather that than leaks in transit.

Limitations and caveats

• Not for oily or waxy substrates: If the wood has ever seen a heavy oil sealer, penetration can be poor. Stripping is mandatory or choose a like-for-like product.
• Thin coats only: Over-application or allowing product to pond will slow cure and can lead to temporary tackiness or a whitish blush if moisture sits on a wet surface. Wipe excess during application and avoid late-day dew.
• Cure time matters: Walkable may be hours; fully resilient takes longer. Give it 24–48 hours when possible, especially before heavy use.
• Clear isn’t color-preserving forever: It slows graying but doesn’t stop it. If long-term color retention is paramount, consider a lightly tinted version in the same system.
• Not a traction enhancer: It doesn’t add grit. If you need slip resistance on steps, address that mechanically (profiled treads) or with separate non-skid solutions.

Tips for best results

• Moisture check: Aim for under 15% wood moisture content.
• Surface prep: Clean, rinse thoroughly, let dry, then sand to open pores. Wipe away dust with a barely damp cloth right before finishing.
• Timing: Apply in the warmest, driest part of the day. Avoid imminent rain or evening dew.
• Technique: Two light, wet-on-wet coats; back-brush; remove any puddles within a few minutes.
• Maintenance: Clean annually. Recoat high-wear horizontal areas when water stops beading uniformly.
• Storage: Don’t let it freeze. Stir well before use; if you see hard separation that won’t reincorporate, don’t use it.

Who it’s for

• Ideal: Dock owners, lakeside decks, piers, and outdoor furniture where low odor, aquatic safety, and easy maintenance matter.
• Good fit: Thermally modified wood and dense species once properly sanded.
• Not ideal: Surfaces previously treated with oil/wax sealers unless fully stripped; users wanting a glossy, film-forming finish; projects where cure time cannot be respected.

The bottom line

Seal-Once Marine is a smart choice for water-adjacent projects that need a breathable, clear sealer with minimal odor and easy cleanup. It rewards good prep and thin, methodical application with reliable water repellency and a natural, non-plastic look. It’s not the cheapest route, and it won’t rescue wood that can’t accept a penetrating finish, but used as intended it’s effective and low-maintenance.

Recommendation: I recommend this sealer for docks, decks, and outdoor furniture where environmental safety, low odor, and a natural appearance are priorities. Choose it if you’re willing to do proper prep and apply two light coats in favorable conditions. If you need a high-gloss film, want to apply over old oil, or can’t allocate adequate cure time, consider a different system. For everyone else working near water, this is a dependable, responsible finish that does the job without drama.