It's what archeologists say could be the most significant haul of gold, and information, from a shipwreck of the Byzantine era: a ship discovered more than a decade ago on the seabed off Croatia's southern coast was probably carrying a high-ranking person and his entourage, judging by the gold jewellery found in the wreckage.

Announcing the results of their decades-long underwater excavation for the first time on Thursday, archeologists said the shipwreck could be dated to the 7th or 8th century and that the artifacts on board indicated that this was no ordinary merchant vessel.

These included gold coins dating to the Heraclius dynasty of four emperors, buckles decorated with rubies, emeralds and pearls, and a golden signet ring with a picture of the emperor "that certainly wouldn't be worn by just anyone," said Pavle Dugonjic, head of the Department of Underwater Archeology at the Croatian Conservation Institute.

His team, equipped with diving gear, has spent the past decade slowly uncovering the history of the ship, whose wreckage lies near the Adriatic island of Mljet.

"This is an impressive amount of gold, the largest ever found on a shipwreck in the entire Mediterranean," said Igor Miholjek, the head of research at the Croatian Conservation Institute.

"It weighs over 600 grams when weighed after cleaning and restoration."

"For me, it's the most important shipwreck of its period," said Justin Leidwanger, professor of archeology at Stanford University.

"If you're studying the end of the late Roman Empire and the transformation into the medieval world, this is a critical site for us to understand and to gain insights into how the Mediterranean was held together by its sea routes, how it fragmented, how the empire fell apart."

The Byzantine Empire, successor to the Roman Empire and centered on Constantinople, now Istanbul in Türkiye, once dominated the eastern Mediterranean but by the early 8th century was mired in turmoil and was losing territory.