I was reading an article on the receover of the seventeenth century royal Swedish ship, the Vasa.  I found it interesting that after it sank in on its maiden voyage in the 1620s, an attempt was made to recover items from it:

Days after the Vasa sank, Sweden’s Council of the Realm sent a British man down to salvage the wreck, but the mission failed. In 1663, a Swede named Albrecht von Treileben plunged into the chilly ström under the protection of a diving bell and managed to retrieve more than 50 of the ship’s expensive bronze cannons.

There was even an illustration of what this looked like.  I didn’t know that underwater reclamation like this took place almost 400 years ago.