Eastbourne, England (Yankee go home!)
Only one hexside (NE) is a river hexside, correct?
I couldn't tell if the river wrapped west as well with the green hex perimeter.
Looking at the 'real' map from the game, rather than the VASSAL and/or Cyberboard map, all three hexsides for Calcutta are river, the other three are, of course, sea hexsides.
But this is also evident on the 'new' Cyberboard map, so I'm not sure what you are looking at to be missing the visual of all three hexsides being river. Two of them are the Ganges river, and the other one to the NE is not labeled.