Reef-safe sunscreen

Sunscreen washes off swimmers in large quantities - and some of its common chemical filters, especially oxybenzone and octinoxate, are proven to stress coral, disrupt its reproduction, and worsen bleaching. Thailand banned sunscreens containing harmful chemicals in all its marine national parks in 2021, with fines for violations; this applies on trips to Ang Thong and other parks around Samui. The practical rule of thumb: choose 'reef-safe' mineral sunscreens based on zinc oxide or titanium dioxide (non-nano), and check the ingredients list rather than trusting front-label marketing, since 'reef-safe' is not a regulated term. Even better is reducing sunscreen need altogether: a long-sleeve rash guard or swim shirt plus hat covers most skin and washes nothing into the sea. Apply any sunscreen at least 15-20 minutes before entering the water so it binds to skin rather than rinsing straight off.

Dates

Marine park sunscreen rules from 2021

Highlights

• Thailand banned harmful sunscreen chemicals in marine national parks (2021)
• Avoid oxybenzone and octinoxate; choose zinc oxide or titanium dioxide
• 'Reef-safe' is not a regulated term - read ingredients
• Rash guards reduce sunscreen need and protect from sun and stings

Local tips

• Apply sunscreen 15-20 minutes before swimming so it absorbs
• A long-sleeve swim shirt is the most reef-friendly 'sunscreen' of all

Frequently asked questions

Is reef-safe sunscreen required on Samui boat trips?

Inside marine national parks like Ang Thong, sunscreens with certain harmful chemicals have been banned since 2021. Mineral-based sunscreen or a rash guard is the safe choice.

Which sunscreen ingredients harm coral?

Oxybenzone and octinoxate are the main proven offenders. Non-nano zinc oxide or titanium dioxide are the preferred alternatives.