The man, identified as Shlomi Katzin, was on a dive Saturday in northern Israel when he came upon a trove of ancient artifacts including pottery, anchors and the nearly 4-foot-long sword, Israel’s Antiquities Authority said Monday.
The diver took the sword back to the shore – fearing the find could be buried – and gave it to the Israel Antiquities Authority's Northern District Robbery Prevention Unit inspector.
"It was found encrusted with marine organisms, but is apparently made of iron," Nir Distelfeld, an inspector in the authority’s robbery prevention unit, told The Associated Press on Tuesday. "It is exciting to encounter such a personal object, taking you 900 years back in time to a different era, with knights, armor and swords."
The area where the sword was found reportedly provided shelter for ancient ships and is the origin of many archaeological treasures dating back thousands of years.
"The archaeological finds at the site show that it served as a small, temporary natural anchorage for ships seeking shelter. Identification of the various finds shows that the anchorage was used as early as the Late Bronze Age, 4,000 years ago. The recent discovery of the sword suggests that the natural cove was also used in the Crusader period, some 900 years ago," Kobi Sharvit, director of the Israel Antiquities Authority's Marine Archaeology Unit, said in a statement posted to Facebook alongside a video of the sword and other artifacts.
The Crusades ran from the late 11th century through the late 13th century.
The shell-encrusted sword is set to be cleaned and further analyzed.
Katzin was awarded a certificate of appreciation for good citizenship.
Israeli law requires any artifacts found to be returned to the country.
The Associated Press contributed to this report