Just a heads up. The city of Pavlopetri, now sunk off the coast of Laconia, southern Greece, has been surveyed by submarine archaeologists, revealing a long history dating to c. 2800 BCE, long before the Mycenaean period. It was probably a major trading hub and the analysis of the many discovered artifacts (pottery, etc.) is now being take care of.
The earliest dates may be the most interesting ones, in my opinion, because they correspond chronologically with the pre-Indoeuropean Cycladic and Minoan cultures, of which only so much is known. However we will have to wait until the archaeological work is finished.
More at Science Daily, including a video and a podcast.