Koh Phangan sunscreen rules, UV and reef-safe snorkelling

The sun here is stronger than most people expect

Villa Ullassa sits at 9.7° north. That means the sun passes almost directly overhead at midday, and the difference between the sun at 10.00 and the sun at 13.00 is much sharper than it is in Europe. Thailand's UV index averages around 11 to 12, which sits in the "extreme" band of the WHO scale, and Surat Thani — the province Koh Phangan belongs to — is one of those where readings climb into the very high to extreme range from about 10.00 onwards.

Two practical consequences. First, an hour on a longtail boat with no shade will burn you even on a hazy day, because cloud filters heat far better than it filters UV. Second, the water works against you: swimming and snorkelling put your back and the tops of your calves under direct sun, reflected light adds to the dose, and most sunscreen is gone long before you think it is.

The unglamorous fixes are the ones that work. A long-sleeved rash vest is the cheapest, most reliable sun protection on the island and removes the need to reapply anything to your back every forty minutes. A hat with a real brim beats a cap. And if you are on a boat trip, ask before booking whether there is shade on board — many of the smaller Ang Thong and Sail Rock boats have very little.

The rule that can cost you money

Thailand's Department of National Parks, Wildlife and Plant Conservation has banned sunscreens containing four chemicals from all marine national parks: oxybenzone (benzophenone-3), octinoxate (ethylhexyl methoxycinnamate), 4-methylbenzylidene camphor and butylparaben. The ban was issued under the 2019 National Park Act and carries a maximum fine of 100,000 baht. It is not a dormant rule that everyone has forgotten about, either — the department publicly restated the warning to tourists in October 2025.

From Koh Phangan this matters mainly on two kinds of trip: a day out to Mu Ko Ang Thong, and anything inside Than Sadet–Ko Pha-ngan National Park, which covers a stretch of the island's own north-east coast and waterfalls. Bleaching surveys in 2024 recorded damage inside both parks.

In practice, nobody is going to search your bag at the pier. But the sensible move is to read the ingredient list on your own bottle before you pack it rather than after you arrive, because oxybenzone and octinoxate are still common in familiar Western brands. If yours contains them, leave it at home.

What to use instead

The standard advice from Thai authorities and dive operators is a mineral sunscreen — zinc oxide, or zinc plus titanium dioxide. Be sceptical of the words "reef-safe" on the front of the bottle: the term is unregulated and means whatever the manufacturer wants it to mean. The ingredient list is the only thing worth reading. There is now also a Reef Protection Factor (RPF) certification appearing on some products sold in Thailand, though availability is patchy.

Buying on the island is possible but not effortless. Convenience shops and pharmacies in Thong Sala stock plenty of sunscreen, but much of the Thai domestic market is aimed at faces rather than bodies, often with whitening or brightening claims, and Thai labelling caps SPF claims at 50+ with a separate PA rating for UVA. Zinc-based body sunscreen is easier to find in dive shops in Chaloklum and along the west coast than in a supermarket. If you have a brand you like and a bottle you trust, bring it.

What is actually happening to the reefs

This is worth understanding, because it changes how you use the advice above.

Koh Phangan's reefs are unusually well documented for the Gulf of Thailand, thanks to a long monitoring programme based in Chaloklum. A 2023 study analysing seven reefs around the island between 2014 and 2022 found a genuinely encouraging pattern: rapid recovery, driven largely by fast-growing plate-like hard corals.

Then came 2024 and the fourth global mass bleaching event. Researchers surveying three sites around the north-west of the island — Ao Thong Lang, Haad Salad and Mae Haad — recorded sea surface temperatures averaging 0.54°C higher than the year before, with accumulated heat stress passing the threshold associated with widespread bleaching and mortality between May and July. Almost 45% of coral colonies bleached, and live hard coral cover fell by 19% compared with February. By October there was partial recovery.

So: heat is the main threat to these reefs, not your sunscreen. Anyone telling you that changing bottles will save the coral is overselling it. The reason to change anyway is that heat stress is exactly the situation in which you avoid adding any further pressure — and that the reefs here have shown they can bounce back when left alone.

The other rules, and the one that gets broken most

Since December 2018, the Department of Marine and Coastal Resources has had published rules covering marine activities around Koh Samui, Koh Phangan and Koh Tao. Boats may not anchor in coral areas and must use existing mooring buoys; dumping rubbish or waste water at sea is prohibited; feeding fish or other marine animals in reef areas in order to catch them is prohibited; and sea walking is banned. Penalties run to up to a year's imprisonment, a fine of up to 100,000 baht, or both.

The rule broken most often is not in that list, because it is not a law: don't stand on coral. On the island's best shore snorkelling — the sandbank out to Koh Ma at Mae Haad, the reef at Haad Khom, the fringing reef off Haad Salad — the coral sits shallow enough at low water that fins and feet reach it easily. Go closer to high tide, wear a rash vest instead of reaching for more sunscreen, and keep vertical distance rather than horizontal distance.

From the villa

Villa Ullassa's own west-facing terrace has the useful quality of being in shade by the time the light gets good, and the pool is a gentler place to spend the 11.00 to 15.00 window than any beach on the island. If you are planning snorkelling days, we can tell you which bays are reading clear that week — visibility on this coast changes quickly after heavy rain. More island practicalities are collected in our journal.