Palau's president Tommy Remengesau is set to sign a law turning most of the country's waters into a marine sanctuary, which will be one of the biggest in the world.
The sanctuary will be about the size of California — making it the world's sixth largest area in which commercial fishing and oil drilling will be banned.
More than a year after it was first announced, the marine park will be signed into law this week after Palau's congress passed the bill.
Seth Horsmeyer from The Pew Charitable Trusts, which provided technical support on the project, said the people of Palau support the sanctuary.
"A testament to how much support there is here, especially from Palau's local fishermen, is that no-one voted against it in either house of the congress," he told Radio Australia's Pacific Beat.
The 500,000-square-kilometre reserve covers 80 per cent of Palau's territorial waters.
Mr Horsmeyer said there would be tight rules surrounding the sanctuary.
"Once it's fully implemented, there are strict rules for how you need to move through Palau's waters," he said.
"You can't have your fishing gear out, you have to go in a straight line at a certain speed — all these kinds of things that help make monitoring and enforcement simpler."
Mr Remengesau said his country will promote scuba diving, snorkelling and eco-tourism as an alternative income to commercial fishing.
"We're not just closing our waters and throwing away the key," he told a UN oceans conference last year.
"We're closing our waters because we will do our part in making sure that there's healthy stocks of fish in Palau that can migrate to other places, and that there are other options to grow the economy.
"These are important ways to make a living and at the same time preserve the pristine environment that we have been blessed with in Palau."