Hi there Argonaut.
If you have a passion for both archaeology and diving, the place to go in the Thyrrenian sea is Napoli (Naples), which is some 4 hours drive south from Htsprosoft's environs (and mine).
Napoli offers the National archaeological museum there is simply awesome, the roman town of Pompeii (still intact after 2 thousand years) is fantastic, and underwater, you may dive the ancient roman town of Portus Julius which is right in front of today's city.
Please let me know if you're interested in more details and directions for an eventual trip.
Some links:
Naples nation museum of archaeology:
Museo Archeologico Nazionale, Naples (Photo Archive)
Pompeii:
Soprintendenza archeologica di Pompei
A view of the submerged roman town of Portus Julius, Baia, Naples:
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