Smithsonian Institution
Smithsonian Learning Lab: Decoding the Past: The Work of Archaeologists
Through this study, students will think like an archaeologist, and move towards a better understanding of our world by taking a look back at civilizations of the past.
BBC
Bbc: History: An Introduction to Marine Archaeology
A very good introduction to the discipline. Provides details on how it is different from land-based archaeology, how wreck sites are investigated, issues regarding "treasure" wrecks, conservation, and much more.