Shipwrecks and hulks are obvious sources of information, and objects, harbours, buildings and structures are also important in building a picture of our past.
Mae'n amlwg bod llongddrylliadau ac ysgerbydau llongau yn ffynonellau gwybodaeth ac mae gwrthrychau, harbwrs, adeiladau a strwythurau hefyd yn bwysig i greu darlun o'n gorffennol.