Mask Defog Options:
Science, Safety, and Why I Recommend Stream2Sea

A foggy mask can turn a good dive into a frustrating one. Even in the clearest water, your experience depends on your ability to see through your mask. Fog is preventable, but the solution you choose matters. Not all defogs are equally effective, environmentally safe, or appropriate for dive use.

There are three common approaches: spit, baby shampoo, and purpose-built defog solutions. I have used all of them, and while they each have a place, only one stands out as the most reliable and environmentally conscious choice.

What Causes Mask Fog?

Fogging happens when warm, humid air from your face condenses on the cooler mask lens. If nothing breaks the surface tension of those droplets, they form a fine mist and scatter light. A proper defog works by reducing that surface tension, allowing moisture to spread in a clear, even layer.

Option 1: Spit

Spit has been the go-to method for generations of divers. It contains natural proteins and surfactants that help prevent fog, and it is always available.

• Pros: Free, biodegradable, no synthetic chemicals
• Cons: Inconsistent performance, easily rinsed off, less effective in cold water or with dry mouth, hygiene concerns

Bottom line: Spit can work, but its fragility and variability make it a poor choice for reliability. It does not tolerate mistakes during kit-up and must be reapplied every time.

Option 2: Baby Shampoo

Example: Johnson’s No More Tears

Baby shampoo is a widely used DIY defog. It contains multiple mild surfactants that reduce surface tension and prevent fogging when diluted.

What’s in it: Cocamidopropyl betaine, sodium cocoyl isethionate, lauryl glucoside, sodium methyl cocoyl taurate, plus fragrance, polyquaternium-10, sodium benzoate, and disodium EDTA.

• Pros: Highly effective when diluted, very low cost, non-irritating to eyes, widely available
• Cons: Not tested for aquatic safety, may leave residue, includes persistent chemicals, requires pre-dilution

Bottom line: Baby shampoo works well but introduces ingredients into the water that are not needed, and it does not hold up to accidental rinses or floods.

Option 3: Stream2Sea Professional Mask Defog

This is the defog I use and recommend. I have tried spit, baby shampoo, and travel boat defogs, and Stream2Sea has consistently performed better in my hands and for the students and buddies I have shared it with.

What’s in it: Sodium lauroyl methyl isethionate, aloe vera extract, guar gum, purified water, and a small amount of alcohol. No dyes, fragrance, or preservatives.

Effectiveness: Applies easily, rinses clean, and holds up better if your mask is dropped in water or floods during the dive.

Environmental safety: Verified lab-tested to be safe for a wide range of aquatic life, including freshwater species, fish, and coral larvae.

• Pros: Reliable, resistant to rinsing, environmentally tested, clean formula, purpose-built for divers
• Cons: Higher cost per ounce, limited in-store availability

Bottom line: Stream2Sea has outperformed all other options in my experience and has solved fogging issues for every diver I have shared it with.

I don’t have any sponsorship or financial tie to Stream2Sea.
I’m just recommending what has worked best for me and for the divers I’ve dived with.

What About Cost? The Myth of the “Cheaper” Option

One of the most common arguments in favor of baby shampoo is price. And yes, it’s inexpensive. But here is the actual breakdown:

• Baby Shampoo: ~$0.01 per dive
• Stream2Sea: ~$0.05 per dive

That’s a difference of about four cents. Now compare that to the cost of diving:

• $20+ for quarry entry
• $20–30 for gas
• $75–100+ for rental gear, or $2000+ in personal gear

The cost difference between defog options is trivial in the context of your dive day. Stream2Sea offers better performance, avoids unnecessary chemicals, and supports both freshwater and marine environmental safety.

Baby shampoo has a long tradition in diving, and it’s what many instructors and dive shops still use. But better options are available now, and switching does not require a significant investment.

Head-to-Head Summary

If your only concern is price, baby shampoo is hard to beat. If you're out of options, spit can work in a pinch. But if you care about reliability, aquatic safety, and consistent results, Stream2Sea is the best choice. I recommend it because I have tested it in real dives and seen it outperform everything else. It works even when the mask is dropped or flooded and has never failed me or the divers I’ve given it to. This is one of the cheapest and easiest ways to improve your dive day. Choose a product made for divers and safe for the water you dive in.