If you're counting Hollywood movies, "the Deep" from 1977 is my favorite sunken treasure movie. Always liked Robert Shaw, he played the old Captain in the original Jaws, and is a similar character in this movie. (1977? ....Yeah, I know, I'm feelin' old. Very good movie, though!).
Some of my favorites
The Deep
Sahara
Fools Gold
Into The Blue
National Treasure
The Perils of Gwendoline
Romancing the Stone
any of the Indiana Jones
The Mummy