[snopercod]

How do they know it's 900 years old, and how do they know that it's a certain ship?

[blam]

"How do they know it's 900 years old?"

"After carbon-dating tests on the ship's wood, a local variety called Anjili, Gopi said, "We believe the ship to be approximately 920 years old."

[LaMudBug]

"How do they know it's 900 years old, and how do they know that it's a certain ship?"

The Holy Ghost descended from heaven and shared his knowledge with them.