A couple of months ago, Lionel Casson died, the author of important works on ancient ships and navigation. The subject is quite important, because naval transport was (and is) cheap, and the Mediterranean world could become integrated into one Hellenistic culture and one Roman Empire because the sea was, in the summers, friendly towards sailors. The flowering of Greece and Rome was only possible because transport and the exchange of ideas was easy. No ships, no classics.
Bill just made available a nice article by Casson, dealing with speed under sail. It’s from 1951, and if you like it, you may like to read Richard Duncan-Jones’ article “Communication Speed and Contact by the Sea in the Roman Empire” in Structure and Scale in the Roman Economy (1990).