When was the locket found on the ocean floor during the titanic

The locket is found on the ocean floor at the end of the movie, Rose throws the necklace into the ocean.

Explanation:

In Titanic, Caledon, fiance of Rose gives the necklace to her as a gift but Rose you was in love with Jack takes it with no other choice. This necklace is used to frame Jack as a thief after Caledon figures about their relationship. Later after years, when the archaeologists try asking her if she knew where the necklace was, she denies because she believed the necklace belonged to the Titanic and Jack though it had been with her all her life. Therefore, she drops the necklace into the ocean believing Titanic was it's place than the museum.