DC - I happen to be on the Hingham ferry now and have a lovely view of Hull. Commute times posted on the MBTA site are accurate. Only severe ice stops the boats in the winter (happens like once every 2-3 years, I believe).
While it's convenient to live in the same town as the public transportation, a short drive to the boat is a fine option too. I'm down in Scituate and drive the 20min to the boat in Hingham and then take it in. Some car time allows me to get coffee, stop for groceries, etc.
Living on the coast is a big of a geographical shocker...there's nothing to your east except Europe. Living in Hull might be even more of a shocker; with the harbor surroudning you on the west as well
If you like the idea of coastal living and commute by boat, Scituate or Marshfield should also be considered. That said, finding somethng with an official in-law may make things pricey. Perhaps a more traditional 2 family in Marshfield(?).
Also, the MBTA is looking at cutting commuter boats to save $$. Nothing official yet, as far as I know, but could happen. Greenbush commuter rail is the newest and next best public transportation alternative....which also happens to terminate in Scituate for an even shorter drive.
best of luck!