The swelling tide of tourists to a Thai island has brought it to the brink of irreversible damage, say Thai officials.

The tourists, in other words, are destroying what they came to see.

This week, the director-general of Thailand’s Department of National Parks, Wildlife and Plant Conservation said that Koh Tachai — an increasingly popular destination, especially for scuba divers — would not reopen after the incoming monsoon season. Koh Tachai is the northernmost of the Similan Islands, in the Andaman Sea, which are known for their idyllic, white-sand beaches, crystalline waters and delicate coral reefs. The Similan Islands are often reached by boat from the giant tourist hub in Phuket.

During peak season, tour companies sell diving packages to tourists who come to the island and support a fledgeling pop-up economy there. According to a Bangkok Post article, a university dean who spoke on Sunday at a tourism fair organised by the Government said 14 companies were still selling packages to Koh Tachai. “A beach on the island can hold up to 70 people, but sometimes the number of tourists was well over 1,000 on the beach, which was already crowded with food stalls and tour boats,” said Thon Thamrongnawasawat, the deputy dean of the fisheries faculty at Kasetsart University in Bangkok. “This caused the island to quickly deteriorate.”

Koh Tachai is part of a national park that is closed off annually to tourists from May to October 15 for the duration of the monsoon season. But now it will be closed indefinitely.

“We have to close it to allow the rehabilitation of the environment, both on the island and in the sea, without being disturbed by tourism activities before the damage is beyond repair,” Tunya Netithammakul, the national parks director, was quoted as saying by the Bangkok Post.

“In fact, Koh Tachai is preserved as a primitive zone, not a tourist site,” said Thon, who was referring to a designation that Thailand gives certain particularly vulnerable areas. “If it’s not closed now, we’ll lose Koh Tachai permanently.”

•Max Bearak writes about foreign affairs for The Washington Post. Previously, he reported from South Asia for the New York Times and others