I’m a marine scientist. I spent decades studying what goes into our waterways — and what comes out of us when we swim in them.
What I found changed how I look at every product I put on my body. And it’s the reason I left coastal engineering to build Miami Beach Bum.
Here’s the truth: sunscreen labels are designed to be confusing. The marketing language is crafted to make you feel safe without actually telling you what’s in the bottle. “Waterproof.” “Reef-safe.” “Dermatologist tested.” These phrases sound like science. Most of them aren’t regulated at all.
This guide is the cheat sheet I wish existed when I was doing water research in Miami. It’s everything I know about sunscreen labels — written so you don’t need a marine science degree to understand it.
Part 1: The Words That Mean Nothing
Before we get to the ingredient list, let’s talk about the marketing language on the front of the bottle. These terms sound official. They are not.
“Waterproof”
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This word is banned. The FDA prohibited the term “waterproof” from sunscreen labels years ago because it’s simply not true. No sunscreen is waterproof. The correct term is water resistant — and even that only holds for 40 or 80 minutes of swimming or sweating, depending on the formula. Any brand still using waterproof language is either unaware of the regulation or banking on the fact that you are. Check the label. If you see it, put it back. |
“Reef-Safe”
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This term is completely unregulated. There is no FDA standard for “reef-safe.” Any brand can print it on their packaging with zero verification, zero testing, and zero accountability. I’ve seen brands with oxybenzone in their formula — one of the most documented reef-harming ingredients in existence — labelled as reef-safe. The only way to know if a sunscreen is genuinely reef-friendly is to flip it over and read the actual ingredient list. We’ll show you exactly what to look for. |
“Dermatologist Tested” and “Clinically Proven”
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These phrases tell you almost nothing. “Dermatologist tested” means a dermatologist looked at the product. It doesn’t mean they approved it, recommended it, or ran any controlled study. “Clinically proven” often refers to a single unpublished study with a small sample size. These are marketing phrases. They’re not lies, exactly — they just don’t mean what most people assume they mean. |
Part 2: The Ingredient List (What Actually Matters)
This is where the real information lives. Ingredients are listed in descending order by concentration — the higher up an ingredient appears, the more of it is in the formula. Here’s how to read what you find.
The Red List — Ingredients to Avoid
These are the ingredients that have documented concerns for human health, marine ecosystems, or both. If you see any of these near the top of a sunscreen label, we’d recommend looking for an alternative.
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Ingredient |
What It Is & Why It Matters |
Verdict |
|---|---|---|
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Oxybenzone |
A chemical UV filter. Detected in human bloodstream after a single application. Associated with hormone disruption and coral bleaching at low concentrations. |
AVOID |
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Octinoxate |
Common chemical filter. Detected in fish tissue in South Florida waters. Classified as an endocrine disruptor in some studies. |
AVOID |
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Octocrylene |
Stabilizes other UV filters. Degrades into benzophenone — a potential carcinogen — over time. Found accumulating in coral tissue. |
AVOID |
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Homosalate |
Chemical filter that disrupts hormone activity. Accumulates in the body faster than it can be eliminated. EU restricts concentration limits. |
CAUTION |
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Polyethylene / Microbeads |
Plastic particles used as exfoliants or texture agents. Non-biodegradable. Detected in marine organisms globally. |
AVOID |
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Nano-particles (any ingredient labelled nano-) |
Ultra-fine particles that penetrate biological membranes. Nano zinc oxide and nano titanium dioxide behave differently from non-nano versions — higher absorption risk. |
AVOID |
The Green List — What to Look For
These are the ingredients that have the strongest safety and reef-compatibility profiles. When these appear at the top of a label, you’re in good shape.
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Ingredient |
What It Is & Why It Works |
Verdict |
|---|---|---|
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Non-nano Zinc Oxide |
A mineral UV filter that sits on top of the skin and physically reflects UV rays. Does not absorb into the bloodstream when non-nano. The gold standard for reef-safe sun protection. |
USE IT |
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Aloe Vera |
Hydrating, anti-inflammatory carrier. Soothes UV exposure and supports skin barrier repair. Biodegradable. |
USE IT |
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Jojoba Oil |
Structurally similar to skin’s natural sebum. Non-comedogenic, deeply moisturising, and reef-compatible. |
USE IT |
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Avocado Oil |
Rich in vitamins A, D, and E. Supports barrier function and protects against oxidative stress from UV. Biodegradable. |
USE IT |
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Shea Butter |
Plant-derived emollient. Anti-inflammatory, hydrating, and stable in sun formulas. |
USE IT |
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Vitamin E (Tocopherol) |
Antioxidant that stabilises formulas and protects skin from free radical damage caused by UV exposure. |
USE IT |
The Grey Zone — It’s Complicated
These ingredients aren’t black and white. Context matters — concentration, nano vs. non-nano grade, and the rest of the formula all affect how these behave.
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Ingredient |
The Nuance |
Verdict |
|---|---|---|
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Titanium Dioxide |
A mineral filter that’s generally safe in non-nano form. However, nano-grade titanium dioxide has higher absorption and marine impact concerns. The label must specify “non-nano”. |
CHECK GRADE |
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Avobenzone |
A chemical filter with less reef data than oxybenzone. Degrades quickly in sunlight unless paired with a stabiliser. Not our top choice but less documented harm. |
PROCEED WITH CAUTION |
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Fragrance / Parfum |
A catch-all term that can mask dozens of undisclosed chemicals. Not inherently harmful but impossible to evaluate without disclosure. Sensitive and acne-prone skin often reacts. |
CAUTION |
Part 3: How to Actually Read a Label in 60 Seconds
You’re standing in the Whole Foods aisle. You have 60 seconds before your kid starts getting restless. Here’s the fastest way to evaluate a sunscreen:
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Step 1: Check the active ingredients first.
Active ingredients are usually listed separately at the top of the label in a box labelled “Drug Facts.” This is the sunscreen part. Look for: non-nano zinc oxide or non-nano titanium dioxide. If you see oxybenzone or octinoxate here, put it back.
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Step 2: Check the water resistance claim.
It should say “water resistant (40 minutes)” or “water resistant (80 minutes).” If it says “waterproof,” the brand isn’t keeping up with FDA labelling rules. Not a great sign.
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Step 3: Scan the inactive ingredients for polyethylene.
This is where microplastics hide. Polyethylene is the most common one. If you see it in a body scrub or exfoliating sunscreen formula, that’s plastic going down your drain and into our waterways.
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Step 4: Ignore the front of the bottle.
Reef-safe, natural, clean, eco-friendly — none of these have legal definitions for sunscreen. The front is marketing. The back is information.
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QUICK REFERENCE: THE 60-SECOND LABEL SCAN AVOID: Oxybenzone · Octinoxate · Octocrylene · Homosalate · Polyethylene · anything labelled nano- LOOK FOR: Non-nano Zinc Oxide · Aloe Vera · Jojoba Oil · Avocado Oil · Vitamin E IGNORE ON THE FRONT: Reef-safe · Waterproof · Natural · Eco-friendly · Dermatologist tested |
Part 4: Why Reapplication Actually Matters
One of the most common sunscreen mistakes — even among people using a good formula — is applying once and assuming they’re covered for the day. Here’s the science:
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SPF measures intensity, not duration. SPF 50 filters about 98% of UVB rays. It does not mean you’re protected for 50 hours, or even 50 minutes.
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Water resistance has a hard time limit. Even the best 80-minute water-resistant formula needs to be reapplied after swimming or heavy sweating. The clock starts the moment you get in the water.
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Towel drying removes sunscreen. Even if you’re not swimming, drying off with a towel takes the sunscreen with it. Reapply after drying.
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UV doesn’t care about clouds. In Miami, the UV index rarely drops below 6 — even in December. UVA rays penetrate cloud cover. Year-round protection matters here more than almost anywhere in the US.
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The rule of thumb: Apply 15 minutes before sun exposure. Reapply every 80 minutes of swimming or sweating. Reapply after towel drying. In Miami, that usually means applying twice on a full beach day. |
Part 5: What This Means for Our Ocean
I built Miami Beach Bum because I couldn’t separate what I knew about ocean chemistry from what I was putting on my skin and my daughter’s skin.
The research is clear: chemical UV filters wash off in the water. They’ve been detected in coral tissue, in fish organs, and in human bloodstream. They accumulate. And in high-use coastal areas like South Florida, the cumulative effect on water quality is measurable.
This doesn’t mean you shouldn’t wear sunscreen. UV exposure causes real harm — skin cancer is the most common cancer in the United States, and South Florida has among the highest incidence rates. The goal isn’t less sunscreen. It’s better sunscreen.
Non-nano zinc oxide is the best solution we currently have. It sits on the surface of the skin, it physically deflects UV radiation, and it doesn’t absorb into the bloodstream or the water column in the same way chemical filters do. It’s what we use. It’s what the science points to.
What We Use at Miami Beach Bum
Every formula we make starts with the same question: what would pass scrutiny from both a dermatologist and a marine biologist? Our sunscreen line is built around non-nano zinc oxide, with aloe vera, jojoba, and avocado oil as carriers.
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Blocked Sunscreen SPF 50 | Non-aerosol spray | 80 min water resistant | Non-nano zinc oxide | Fragrance-free |
Save Face SPF 50 | Sheer mineral serum | Non-comedogenic | 18% non-nano zinc oxide | No white cast |
Bodyguard SPF 30 | Face + body mineral lotion | Aloe + antioxidants | Family-safe | 40 min water resistant |
Available at Whole Foods, Revolve, Nordstrom, and 400+ stores across the US.
The Bottom Line
Sunscreen labels are complicated by design. The industry has little incentive to make them easy to read — because if you understood what was in most formulas, you’d ask harder questions.
You deserve harder questions. Your skin deserves better answers. And so does our reef.
Save this guide. Flip the bottle next time you’re shopping. And if you ever have a question about an ingredient you’ve found, DM us— I’ll answer it.