Is Your Sunscreen Safe for the Ocean? Here’s What You Need to Know Before You Swim

Sunscreen isn’t just a summer staple. In a tropical country like the Philippines, it’s an everyday essential. It’s part of my routine year-round, but even more so on beach days, when the heat makes me want to run across the shore and jump straight into the water. And for the longest time, my only concern was SPF and whether I was protected enough under the sun.

But the more I explored the country’s clear waters and vibrant marine life, the more I started to wonder what I was bringing into the sea with me. If my sunscreen washes off while I swim, could it be harming the very ecosystem I came to enjoy? With those questions in mind, I turned to experts to find out if my sunscreen is ocean-safe and how I can protect both my skin and the sea.

What’s in my sunscreen?

Sunscreens generally fall into two main categories: mineral and chemical. Mineral sunscreens use active ingredients such as zinc oxide or titanium dioxide. As cosmetic scientist Joyce De Lemos explains in a previous Allure Philippines interview, these filters “do not dissolve in solution and need to be evenly dispersed to effectively cover the skin and protect you from UV damage.” 

On the other hand, chemical sunscreens—also known as organic sunscreens—use UV filters such as avobenzone and oxybenzone. These ingredients are typically oil-soluble, allowing them to blend easily into cosmetic formulations and spread smoothly on the skin.

A common misconception, according to Australian cosmetic chemist Michelle Wong, PhD, in her article “More SPF Mythbusting,” is that mineral sunscreens work mainly by acting like a physical shield that reflects and scatters UV rays, while chemical sunscreens primarily absorb UV and convert it into heat.

In reality, both mineral and chemical sunscreens—more accurately described as inorganic and organic UV filters—protect the skin mostly through UV absorption and the conversion of that energy into heat. Mineral filters do scatter a small portion of UV light but most of their protective effect still comes from absorption.

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Potentially harmful ingredients

However, marine biologist Dr. Hyacinth Suarez warned that both chemical and mineral sunscreens can contain ingredients that may be potentially harmful to marine ecosystems.

For chemical sunscreens, UV filters such as oxybenzone, octinoxate, octocrylene, benzophenone-1, benzophenone-8, OD-PABA, 4-methylbenzylidene camphor, and 3-benzylidene camphor have raised environmental concerns.

For mineral-based sunscreens, the concern lies in particle size, particularly when they are nano-sized. Ingredients such as nano-titanium dioxide and nano-zinc oxide may be small enough to be ingested by marine organisms.

How significant is sunscreen pollution?

While issues about sunscreen and marine life have grown in recent years, experts like Dr. Wong, in her article “Is Your Sunscreen Killing Coral Reefs? The Science,” caution that its impact should be understood in context. 

She explained that certain UV filters like oxybenzone and octinoxate can contribute to coral bleaching under laboratory conditions, but she also points out that these tests often use concentrations far higher than what is typically found in the ocean. In most natural environments, sunscreen ingredients are detected in extremely low levels, often in the parts-per-trillion range, where they are quickly diluted by the vastness of the ocean.

Dr. Wong also emphasized in her article that sunscreen is only one of the many pressures on coral reefs. Climate change, rising sea temperatures, overfishing, coastal development, and pollution remain the most significant drivers of reef decline.

How could marine life be affected?

Harmful UV filters from sunscreens have been found in various environments, from coastal waters, rivers, and lakes to sediments, wastewater treatment plants, and even plants and animals, Dr. Suarez noted. Because many of these ingredients don’t break down easily, they may also contribute to decreased fertility and behavioral changes in fish, developmental abnormalities in sea urchins, and inhibited growth in organisms such as algae and seagrasses.

However, Dr. Wong highlighted the fundamental principle in toxicology that “the dose makes the poison,” meaning that any substance can be harmful in large enough amounts. Hence, only if these mineral particles are present above safe thresholds can they potentially harm marine life.

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What sunscreen should I use, then?

Some sunscreens are formulated with ingredients that are considered more suitable for marine environments, said Dr. Suarez. “Mineral sunscreens use compounds such as zinc oxide and titanium dioxide. They are considered reef-safer when formulated as non-nano,” she said.

Non-nano refers to mineral particles that are larger than 100 nanometers (nm). Because of their size, these particles are generally less likely to be absorbed by marine organisms, making them a safer alternative for aquatic lifeforms.

Sun-safe and ocean-conscious always

“As a marine biologist, my main reminder is simple: respect the ocean—it is not just scenery, but a living system that sustains us all,” Dr. Suarez said.

“Respecting the ocean means avoiding contact with corals or marine life while diving or snorkeling, being mindful of waste that can end up as harmful plastics, keeping a respectful distance when photographing wildlife, and never removing marine organisms from their natural habitat, where even small disruptions can affect their survival,” she adds.

There’s nothing to fear in our sunscreens—only a responsibility to be mindful. Swimming can remain a joy when we become aware of what we carry into the water: the products on our skin, the traces we leave behind, and the quiet impact of everyday choices that shape life beneath the ocean.