The Rhode Island laws are very specific (and draconium!) concerning the recovery of underwater treasures:
CHAPTER 42-45.1, Antiquities Act of Rhode Island
SECTION 42-45.1-2: Purpose of chapter. The general assembly of the state of Rhode Island and Providence Plantations hereby declares that the public has an interest in the identification, interpretation, preservation, and protection of the state's archaeological resources including underwater historic properties situated under the navigable waters and territorial seas of the state; that the public has a right to the knowledge to be derived and gained from a scientific study of these resources; and that therefore it is the purpose of this chapter to provide that activities for the identification, preservation, excavation, study, and exhibition of the state's archaeological resources be undertaken in a coordinated and organized manner, with due consideration given to other significant natural and man-made environmental assets, for the general welfare of the public as a whole.
SECTION 42-45.1-3: Definitions.
(1) "Field investigations" means the study of the traces of human culture at any land or water site by means of surveying, sampling, excavating, or removing surface or subsurface objects, or going on a site with that intent.
(2) "Site" means any man-made landform, fort, earthwork, habitation area, burial ground, historic or prehistoric ruin, mine, cave, or other location which is or may be the source of important archaeological data.
(3) "Specimen" means all relics, artifacts, remains, objects, or any other archaeological evidence of a historical, prehistorical, or anthropological nature which may be found on or below the surface of the earth, and which have scientific or historical value as objects of antiquity or as archaeological samples.
(4)
"Underwater historic property" means any shipwreck, vessel, cargo, tackle, or underwater archaeological specimen, or part thereof, including any found at refuse sites or submerged sites of former habitation, that has remained unclaimed for more than ten (10) years on the bottoms of any navigable waters and territorial seas of the state.
SECTION 42-45.1-4: Property and investigative rights of state.
(a) The state of Rhode Island and Providence Plantations reserves to itself the exclusive right and privilege of field investigation on sites owned or controlled by the state, its agencies, departments, or institutions, in order to protect and preserve archaeological and scientific information, matter, and objects. All the information and objects derived from state lands shall remain the property of the state and be utilized for scientific or public educational purposes.
(b)
Furthermore, subject to any local, state, or federal statute, the title to all bottoms of navigable waters within the state's jurisdiction in the territorial sea, and the title to any underwater historic properties lying on or under the bottoms of any other navigable waters of the state, is hereby declared to be in the state, and the bottoms and underwater historic properties shall be subject to the exclusive dominion and control of the state.