There are some nice beaches well north and south of Boston, but relying solely on public transport to reach both them and Boston can be a challenge. Your best bet might be to stay in Manchester-by-the-Sea, where there's a commuter rail stop that goes into Boston and Singing Beach is located a fairly reasonable walk away.

The beaches close in by Boston that are within a reasonable walk from public transportation (Revere Beach, Wollaston Beach) are varying degrees of scruffy and you won't likely want to swim at them. Same's true to a lesser extent at the various South Boston beaches, which are also generally further away from public transportation. They are pleasant to walk, though (keep shoes on at Revere Beach especially, though, as this one can be especially scruffy).

Well,it depends on what you mean by "public transportation" since everything that Bachslunch writes about beaches accessible by city bus and the T is true, though Wollaston Beach and Revere Beach are scruffy in different ways, with Revere being a bit more Coney Islandish and Wollaston more don't-go-in-the-waterish. However, the Clam Box on Wollaston Beach has astonishingly good fried seafood, so there is reason to go there! And Revere Beach has Kelly's Roast Beef, which also has good fried clams.

It is possible to stay on the Cape and visit Boston by the P&B bus from Hyannis, Barnstable, or Sandwich (Canal) for a long daytrip or to visit the Cape from Boston. Buses are hourly.

Do you not want to deal with a car at all?

What you want seems a bit impractical to me. As an alternative, I'd suggest you want until right after Labor Day -- won't matter because most of Sept. in New England is unsuitable for swimming, sunbathing (unless you hit a weird hot spell), but nice for walking on the beach.

Then I would rent a car, drive to Cape Cod and rent a place for the 3-4 days. You'll get some bargains after Labor Day. Then drive to Boston, get rid of the car, and stay in the city, which is a much better way to see the city.

The back-and-forth between beach and city sounds like a pain to me, especially since the close-in shore towns and beaches aren't all that great.

"won't matter because most of Sept. in New England is unsuitable for swimming, sunbathing (unless you hit a weird hot spell), but nice for walking on the beach."

This statement in my experience (Boston 1978-91, Nantucket 1991 to date) is absolutely not true. September is the absolute best month to be at/near the beach. Water temperatures reach their peak roughly the end of the first week in September. There are usually a couple of windy/rainy days, usually associated with hurricanes coming up the coast
(good days to go to Boston for the museums) but this is the month that the locals love best.

Maybe I shouldn't have told you that. Why don't you come in February instead?

Are you willing to rent a car and drive a short distance from beach house to a commuter station (train or bus) to get into Boston?

That opens up a lot of possibilities -- though given the commute time (>1 hour, likely) it would be more like ``day trip to Boston,'' not so much popping in and out.

"Water temperatures reach their peak roughly the end of the first week in September."

What about air temperatures? The average daily high (that's HIGH, not average temp) in eastern MA in Sept. is in the low 70s. If you think that's swimming/subathing weather, then you have far thicker blood than I do.

Ack said - "and Wollaston more don't-go-in-the-waterish." Rolling on the floor laughing!!! I think in the past 30 years it has been safe to swim a few days in late august every couple of years!!!

We often go to your island and other coastal new england towns on the shoulder/off season. September always seems to have significantly better weather then June.

I think there are a few houseboats for rent in Boston that could be fun. Google.

You can stay in Boston for a few days and then take a ferry to Provincetown. No car required, though you may want to rent a bike in PTown. Don't look for a "package". Just do two separate rentals, but you will likely have to stay for a full week on the cape if you really want to go on Abor Day weekend. And it does get pretty cold out there at night.

Nantucket, the Cape and the Vineyard became resorts because they were cool in the summer. It is very inconvenient for modern vacationers because you really can't count on air temperatures much above 70 during the day except for a brief six weeks between Fourth of July and Opera House Cup, mid August.

We would consider a daytime temperature in the 70's to be perfect swimming weather. The water and the air are in equilibrium, and my tongue is not in my cheek. When we used to winter in Naples, FL, we always left by April1 because it was too hot after that. Your mileage may vary.

We have always the best weather on the Cape is in September. (Memories of the Atlantic side of the Cape in June with leg cramps from the cold water)

I agree with Ackislander. You can often swim in September, and it's a nice time because most of the tourists have gone.

Also, to echo what capxxx said, your plan is feasible if you don't mind a short drive to a commuter rail station. As long as you pay attention to the commuter rail schedules, which is limited outside of rush hour, there are both nice beaches and commuter rail from Ipswich, Newburyport, or Gloucester. Manchester-by-the Sea, as bachslunch mentioned, has commuter rail within walking distance to the beach, but as far as I know, there are few vacation rentals and no hotels there. Also, Manchester doesn't allow non-residents to park at the beach in September.

Lots of people from North Shore towns commute into Boston for work every day. The trip will be roughly an hour each way.

If the leg-cramp comment doesn't discourage you from swimming in Sep., nothing will.

We go to the cape most Septembers and always swim in the bay, where there are many other swimmers. The ponds in Wellfleet and elsewhere are also really lovely that time of year.