Koh Kham Underwater Park

Koh Kham is a small island off Sattahip, within day-trip range of Pattaya, that the Royal Thai Navy manages directly, and that management shows up in how you visit it: the navy runs the ferry, sets the fees, and periodically closes the island altogether to let the reef and beach recover from visitor traffic. It reopens on its own schedule, so the single most important thing to check before planning a trip here is whether it’s actually open on your travel dates.

When it’s running, the appeal is straightforward: a short ferry crossing from Samaesan pier lands you on a compact island with a shallow coral fringe close to shore. Snorkeling is the main activity, with visibility good enough on calm days to make out reef fish without diving gear, and a glass-bottom boat option covers anyone who’d rather stay dry. A wooden boardwalk runs along part of the beach, useful for reaching quieter stretches without cutting across the coral itself.

Watch out: Because access depends on a navy-run rotation rather than a fixed calendar, tour listings and old travel blogs are frequently out of date about whether the island is open. Call the pier or check current schedules directly rather than relying on a review from a year or more back.

Insider Tip: Morning ferries reach the island before onshore winds pick up, which matters more here than at most snorkel spots since the reef is shallow and gets stirred up once the water isn’t flat.

The navy’s rotating-closure model is part of a broader conservation effort on this stretch of coast, alongside the coral restoration and marine education work based at nearby Samaesan. It’s the reason the reef here has held up better than many similarly accessible mainland-adjacent snorkel spots, even with steady day-trip traffic when the island is open.

Pair a visit with nearby Koh Samae San or the Thai Island and Sea Natural History Museum on Samaesan Island, both departing from the same stretch of coast.