The water off the Carmel coast remains the same temperature year-round, which helped preserve the iron in the sword. Because the iron was oxidized, shells and other marine organisms stuck onto it like glue, Mr. Sharvit said. The discovery of ancient artifacts has increased as diving has grown in popularity in Israel, he said.
In the Second Crusade, the Muslim commanders defeated Western crusaders at Damascus, said Jonathan Phillips, a professor of the history of the Crusades at Royal Holloway, University of London.
During the Third Crusade, King Philip Augustus of France, King Richard I (also known as Richard the Lionheart of England), and the holy Roman emperor, Frederick I (also known as Frederick Barbarossa), set out to retake Jerusalem. Saladin, the ruler of an area covering modern Egypt, Syria and Iraq, had conquered it in 1187, said Dr. John Cotts, a professor of medieval history at Whitman College in Walla Walla, Wash.
At the time, Pope Gregory VIII tried to inspire Western Christians through “great emotional language” to retake Jerusalem from Muslims, but ultimately the Muslim army maintained control of the city, Dr. Cotts said.
The sword would have been expensive to make at the time and viewed as a status symbol, Dr. Phillips said. It makes sense that it was found in the sea, he said, because many battles were waged near beaches, where Christian soldiers landed and were sometimes attacked by Muslim forces.
“It could have been from a knight who fell in the sea or lost it in a fight at sea,” he said.
When Mr. Katzin found it, he said he was afraid it would be stolen or buried beneath shifting sand, according to a statement from the authority.
The general director of the Israel Antiquities Authority, Eli Escosido, praised Mr. Katzin because “every ancient artifact that is found helps us piece together the historical puzzle of the Land of Israel.” Mr. Katzin was given a certificate of appreciation for good citizenship.