The sunken treasure of Pavlopetri (Assassin's Creed: Odyssey)

Prompt, a problem such license. A hint on the cultist Gods of the Aegean sea is in one of the three treasure chests of sunken temple to the North of Fira. But I only have two 2 of 2 and shows that the area passed. There is no third hint in the destroyed ship, there's just empty.
Can was at whom such problem?