Story highlights Nearly 2,000 gold coins had sat at the bottom of the sea for around 1,000 years

Divers exploring the ancient harbor of Caesarea came across the treasure

Most of the coins are from the Fatimid Caliphate that once ruled parts of the region

(CNN) The divers initially thought the gleaming object they noticed on the seafloor off the Israeli coast was a toy coin from a game.

But they quickly realized they had stumbled across something a whole lot more valuable in the ancient Mediterranean harbor of Caesarea.

Their chance discovery a few weeks ago led to a trove of nearly 2,000 gold coins that had languished at the bottom of the sea for about 1,000 years, the Israel Antiquities Authority said Tuesday.

It's the biggest hoard of gold coins ever discovered in Israel -- and it could lead to further archaeological finds.

"There is probably a shipwreck there of an official treasury boat which was on its way to the central government in Egypt with taxes that had been collected," said Kobi Sharvit, director of the Marine Archaeology Unit of the antiquities authority.