Water-resistant sunscreen has had its SPF measured after 40 or 80 minutes in water, by a test set out in FDA rules, and the front of the pack must say which: "Water Resistant (40 minutes)" or "Water Resistant (80 minutes)." No sunscreen is waterproof, since US labels may not use the word, so reapply after those minutes of swimming or sweating, immediately after towel drying, and at least every 2 hours.
On a water resistant sunscreen, the number in parentheses is easy to read as a timer, as if protection runs for 80 minutes and then stops. And when sunscreen still comes off in the pool, people doubt the claim. Both treat the number as a promise about your day, when it is a lab result, and sunscreen does come off, which is why the label tells you when to reapply. The SPF (sun protection factor, the number that rates protection from sunburn) printed on the front is the one measured after the time in the water, and 80 minutes is the most a US label can claim.
This page covers US labels only. It reads the FDA's sunscreen labeling rule itself (21 CFR 201.327), alongside guidance from the FDA and the American Academy of Dermatology (AAD). It covers what the test does, why nothing is waterproof, how to check a label, swimming, reapplying, how much to use, and babies. The one note about our own product is at the end.
What is water resistant sunscreen?
Water resistant sunscreen has its labeled SPF measured after 40 or 80 minutes in water.
A US label can make only two water-resistance claims: "Water Resistant (40 minutes)" and "Water Resistant (80 minutes)." For the 80-minute claim, the rule says "the labeled SPF should be determined after 80 minutes of water immersion," and the 40-minute claim works the same way with 40. So on a water-resistant product, the SPF on the front is not a dry-skin number. It is the figure measured after the water time.
The FDA puts it in everyday terms: the claims "tell you how much time you can expect to get the labeled SPF-level of protection while swimming or sweating." That is the time the test covered, not a countdown on your skin, and the label pairs it with the same two words when it tells you when to reapply: swimming or sweating.
The claim is also optional. As the AAD notes, "Not all sunscreens offer water resistance." A sunscreen without one of the two phrases on the front has not made the claim.
Is any sunscreen actually waterproof?
No. A US sunscreen label is not allowed to say "waterproof", and the rule names the word outright:
There are claims that would be false and/or misleading on sunscreen products. These claims include but are not limited to the following: “Sunblock,” “sweatproof,” and “waterproof.” These or similar claims will cause the product to be misbranded under section 502 of the FD&C Act (21 U.S.C. 352).
U.S. Government Publishing Office · read word for word on This paragraph names three words a US sunscreen label cannot use, and says the list is not complete: similar claims are treated the same way.
The FDA's consumer guidance puts it plainly: "All sunscreens eventually wash off." When the agency wrote this list into the rule in 2011, it described the three terms as "exaggerations of performance" that it did not think could be substantiated. The AAD says the same of "waterproof" and "sweatproof": manufacturers are not allowed to use them.
Is sunblock different from sunscreen? Not on a US label. The rule requires the word "sunscreen" as the product's identity, and "sunblock" is on the barred list.
FDA consumer guidance also says products may not claim protection for more than two hours without reapplying.
So if you are searching for the best waterproof sunscreen, there isn't one. The closest real thing is a label that says "Water Resistant (80 minutes)."
What is the difference between 40 and 80 minutes?
The 80-minute test doubles the time spent in the water before the SPF is measured.
Both versions follow the same pattern in the rule: rounds of moderate activity in water, with rests out of the water in between, and no towel at any point.
| Step | 40-minute test | 80-minute test |
|---|---|---|
| Before the water | Apply a fixed, measured layer (2 mg per square centimeter of skin) and wait at least 15 minutes | Same |
| In the water | 20 minutes of moderate activity | Same |
| Rest | 15 minutes out of the water. "Do not towel" | Same |
| In the water | 20 minutes of moderate activity | Same |
| Rest | None | 15 minutes out of the water. "Do not towel" |
| In the water | None | 20 minutes of moderate activity |
| Rest | None | 15 minutes out of the water. "Do not towel" |
| In the water | None | 20 minutes of moderate activity |
| At the end | Dry completely without toweling, then the SPF is measured | Same |
| Total time in water | 40 minutes | 80 minutes |
The rule also sets the venue: an indoor fresh-water pool, whirlpool or hot tub at 23 to 32 °C (about 73 to 90 °F). The product is tested on enough people to give at least 10 valid results. A US label can claim 40 or 80 minutes, and those are the only two options.
Which sunscreen is the most water resistant?
Look for "Water Resistant (80 minutes)": it is the highest claim a US label can make.
The claim belongs to the finished product that was tested, not to an ingredient or a type of filter, so the label is the only place to find the answer. That includes mineral sunscreens: a zinc oxide or titanium dioxide product is water resistant only if its label says so. Two products that both claim 80 minutes are equal as far as the label goes; it does not rank them.
The AAD's view is that any type of sunscreen can protect you if it is broad spectrum, water resistant, and SPF 30 or higher. Broad spectrum is a label term: the product's UVA protection was also measured, by a test in the same FDA rule, and met that rule's bar. SPF on its own rates only protection from sunburn.
How do I know if my sunscreen is water resistant?
Check two places on the pack: the front, and the Drug Facts directions.
- The front of the pack. A water-resistant product must print "Water Resistant (40 minutes)" or "Water Resistant (80 minutes)" on the principal display panel, the part of the label most likely to face you on a store shelf.
- The Drug Facts directions. The reapply line names the same minutes: "reapply: after 40 minutes of swimming or sweating" (or 80), then "immediately after towel drying" and "at least every 2 hours."
- A product without the claim says so. Its directions read "reapply at least every 2 hours" and "use a water resistant sunscreen if swimming or sweating." That second line is the tell.
- Online, open the label image too. If you look a product up in a text database such as DailyMed, the National Library of Medicine's archive of drug labels, open the label image as well. The text version can leave out the front panel, which is where the claim is printed.
What the water test doesn't measure
The test does not include the sea, surf, sand, toweling, or water time past 80 minutes. It runs indoors in fresh water, as the rule sets out:
The following procedure should be performed in an indoor fresh water pool, whirlpool, and/or hot tub maintained at 23 to 32 °C. Fresh water is clean drinking water that meets the standards in 40 CFR part 141.
U.S. Government Publishing Office · read word for word on This sets where the water-resistance test is run, and defines the water it uses.
Toweling is excluded outright: each rest is "Do not towel," and the skin dries on its own at the end. Every water-resistant label lists "immediately after towel drying" as its own reapply trigger.
The longest test is 80 minutes of water time. So how long does water-resistant sunscreen last? The minutes on the label are water time in a test, not a guarantee for your day. The label's reapply line, below, sets the limits.
The AAD's own advice is stricter than the label's: reapply "immediately after swimming or sweating."
What sunscreen should you use for swimming?
For swimming, use a sunscreen that is broad spectrum, SPF 30 or higher, and water resistant.
Those are the AAD's three checks, and they are the same whether you are heading to a pool or the beach. The label does not change with the venue either: its reapply triggers read the same in both places. If you will be in the water for a while, an 80-minute claim gives you more water time before the label asks you to reapply.
So the answer to "best sunscreen for swimming" is not a brand name: it is any sunscreen whose label shows all three.
If you are buying sunscreen in Hawaii, state law bars the sale, offer for sale or distribution for sale of sunscreen containing oxybenzone or octinoxate without a prescription. Hawaii's sunscreen law sets out what that covers, including where a county rule goes further.
The reapply line on a water-resistant label
A water-resistant label gives three reapply triggers, and whichever comes first applies:
- After 40 or 80 minutes of swimming or sweating, matching the claim on the front.
- Immediately after towel drying.
- At least every 2 hours.
The directions also say to apply 15 minutes before sun exposure. The test works the same way: it waits at least 15 minutes after applying before anyone goes in the water.
None of these triggers is a promise that protection lasts that long in real conditions. They are the latest points the label allows. If you follow the AAD's stricter advice above, you reapply as soon as you are out of the water.
How much to put on before you swim
At least a teaspoon for the face alone, and at a minimum about an ounce, roughly a shot glass, for all the skin clothing leaves bare.
| Area | AAD guidance |
|---|---|
| Face | At least 1 teaspoon |
| Skin not covered by clothing | At a minimum, about 1 fl oz for most adults, roughly a shot glass |
The AAD adds: "Depending on your body size, you may need more sunscreen to protect your exposed skin from the sun's harmful rays." The FDA gives a similar figure: at least one ounce, about a shot glass, for an average-sized adult or child to cover the body from head to toe. For reference, the rule's SPF test uses a fixed layer of 2 milligrams of sunscreen per square centimeter of skin.
Those amounts may look large: the Academy notes that many people apply only about 20 to 50 percent of the amount needed to reach the SPF on the label.
Babies under 6 months: ask a doctor first
The FDA's sunscreen labeling rule requires the same line on every label it covers: "children under 6 months of age: Ask a doctor." The FDA says sunscreen "is not recommended for infants under six months old," and the AAD's advice is to avoid exposing babies younger than 6 months to the sun where possible. A water-resistance claim does not change any of that.
Where Solvyn Shield fits
Solvyn Shield (labeled Solvyn Mineral Sunscreen SPF 50) makes the 80-minute claim. Here is what its label says on the points this page covers, read the way this page reads any label:
- Broad Spectrum SPF 50.
- Water Resistant (80 minutes), printed on the front panel. The Drug Facts label on DailyMed does not include the front panel in its text version, so open the label image to see it.
- Zinc oxide 17.50% is the only active ingredient.
- The directions carry the 80-minute reapply line and "Children under 6 months of age: ask a doctor."
Shield's 80-minute claim is made under the same rule as every other, so everything in the section on what the water test doesn't measure applies to Shield too. Shield claims 80 minutes, the highest a US label allows, and this page claims nothing beyond it.
Solvyn Shield comes in sealed single-use sachets.
Sources
Regulation
- 21 CFR §201.327: Over-the-counter sunscreen drug products; required labeling based on effectiveness testing. Paragraph (a)(2) sets the two water-resistance statements for the principal display panel; (a)(1) and (j) the Broad Spectrum statement and its test; (b) the word "sunscreen"; (e)(1), (e)(3) and (e)(4) the directions; (g) the barred claims; (i)(3), (i)(4) and (i)(7) the test subjects, application and water-resistance procedure. U.S. Government Publishing Office, 2025 annual edition. eCFR lists no substantive change to the section since 29 November 2016.
- 21 CFR §201.60: Principal display panel. The definition of the principal display panel. U.S. Government Publishing Office, 2025 annual edition.
- 76 FR 35620, 17 June 2011: Labeling and Effectiveness Testing; Sunscreen Drug Products for Over-the-Counter Human Use. The final rule that codified §201.327(g), and the FDA's reasoning for it. Federal Register.
FDA guidance
- Sunscreen: How to Help Protect Your Skin from the Sun. FDA's consumer page on water resistance, how much to apply, and infants.
- Tips to Stay Safe in the Sun: From Sunscreen to Sunglasses. FDA Consumer Update on what the 40- and 80-minute claims tell you and which claims are not allowed.
Clinical bodies
- How to select a sunscreen. American Academy of Dermatology.
- How to apply sunscreen. American Academy of Dermatology: amounts for the face and body, and when to reapply.
- Sunscreen FAQs. American Academy of Dermatology: the three checks, sunscreen types, babies, and that many people apply only about 20 to 50 percent of the amount needed to reach the SPF on the label (read 11 October 2026).
State law
- HRS §342D-21. Hawaii's statute on the sale of sunscreen containing oxybenzone or octinoxate. Hawaii State Legislature.
The product label
- Solvyn Mineral Sunscreen SPF 50: Drug Facts label on DailyMed. The Drug Facts label as published on DailyMed, U.S. National Library of Medicine. SPL set ID b0a8d028-87d2-4339-8879-c62cbf8415f2, NDC 87777-948-00, label information updated 15 June 2026.
- Label image (Label2.jpg). The full printed label, including the front panel that the text version leaves out.
All quoted text and figures above were read from these records on 24 September 2026.
A note on scope. This article covers US sunscreen labels only and reflects sources read on 24 September 2026. It is general information, not medical advice. For a baby, a skin condition or anything specific to you, ask a doctor.
Solvyn makes Shield, which means we have an interest in this subject. We have kept the product to one section, and each label fact in it can be checked against the Drug Facts label and label image on DailyMed, linked above. Our guide covers how to apply Shield, step by step, with its full ingredient list.
