As fckwalm said, anywhere along the Treasure Coast. However, you cannot remove anything from a marked wreck site. There are guidelines as to how far away from a site you must be before removing items. I'm unsure of the specifics though.
I always thought under/around the Blue Heron bridge in West Palm would be a good place to look for jewelry. People go to swim and snorkel here all the time, there is even a life guard on duty. At slack tide the water is nice and clear.