The version covered here is the US Hyalu Cica Water Fit Sun Serum UV, sold as broad spectrum SPF50; if your tube has a different name or formula, check its own directions rather than transferring claims between versions.34

What would confirm water resistance?

On US sunscreen packaging, look for an explicit water resistant claim with either 40 minutes or 80 minutes. Those times describe tested protection during swimming or sweating. Neither a watery texture nor a hydrating description supplies that information. Skin1004 describes a light, watery serum texture, which is a texture description rather than a swimming qualification, despite the aquatic ambitions of the name Water Fit.23

Check the front of your tube and the directions on its box before choosing it for wet conditions. Skin1004 updates ingredient lists and identifies the packaging as the place to find the latest list, giving the box a second career as required reading. For a product bought outside the US, read its own label for differences. If the packaging gives no water resistance duration, do not assume either 40 or 80 minutes.234

Does SPF50 mean it stays on in water?

Broad spectrum means protection against UVA and UVB, the two forms of ultraviolet radiation covered by that claim. Water resistance is a separate tested claim. A high SPF number cannot substitute for a water resistance time, and SPF does not tell you how many hours you can stay in the sun.4

Even a sunscreen labelled water resistant is not waterproof. All sunscreens eventually wash off. A 40 or 80 minute rating does not remove the need to reapply, and US sunscreen labels cannot claim that a product is waterproof or sweatproof.24

How should you use the Sun Serum?

  1. 1Apply the Sun Serum as the last step of basic skincare. Skin1004 tells you to spread it evenly over exposed areas, including your face, neck, arms and legs.
  2. 2Apply liberally 15 minutes before sun exposure. Cover exposed skin rather than just the centre of your face; commonly missed areas include ears, the back of the neck, hands and tops of feet.
  3. 3Reapply at least every two hours. For swimming or sweating, use a sunscreen with an explicit water resistance rating and follow its reapplication directions, including after swimming or sweating.
  4. 4Use shade and protective clothing alongside sunscreen. A hat, sunglasses and covered skin provide additional protection rather than leaving every job to the product.
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What should you choose for a beach day or workout?

Choose broad spectrum SPF30 or higher with a stated water resistance rating for outdoor activities involving swimming or sweating. The same selection makes sense for travel that includes pools or active days outside, even when the itinerary calls everything relaxation. Sun protection also matters in winter: snow reflects UV, and activities at higher altitudes can increase sunburn risk. Cold weather is not a reason to skip protection.56

When should you stop using it?

Do not apply this Sun Serum to damaged or broken skin. Keep it out of your eyes, and rinse with water if it gets into them. Stop using it and ask a doctor if a rash occurs. For children under six months, ask a doctor before use.1

Where this answer comes from

  1. 1dailymed.nlm.nih.govdailymed.nlm.nih.gov
  2. 2Questions and Answers: FDA announces new requirements for over-the-counter (OTC) sunscreen products marketed in the U.S.fda.gov
  3. 3Hyalu-Cica Water-Fit Sun Serum UVskin1004.com
  4. 4Sunscreen: How to Help Protect Your Skin from the Sunfda.gov
  5. 5Why you need sun protection in the winteraad.org
  6. 67 travel skin care tips from dermatologistsaad.org