You can take commuter rail train from North Station to Manchester-by-the Sea, and walk approximately half a mile to a nice beach in a small town. The train ride will take you roughly an hour each way, and the trains don't run often outside of rush hour. Lots of people do this trip from Boston in the summer, but fewer on weekdays.

You can also take the same train to Gloucester and go to Good Harbor beach, which often has bigger waves. (They have surfers.) You can catch a local bus or cab to the beach. It would be about 2 1/2 miles to walk there, so that's also an option.

I don't think you can get a beach with big waves AND no chance of undertow. Good Harbor definitely has undertow at times. People, including kids, still swim there all the time. Manchester-by-the Sea's Singing Beach usually has smaller waves.

Have you got a hotel yet? It matters for other suggestions.

Boston is famous for its history; for its architecture, both buildings and landscape; and for its art and music. August is the low point in the Boston music year because the classical organisations are out of town at various festivals (Tanglewood, Rockport Chamber Music) and the rockers are all on summer break.

Boston is a terrific place to walk around. The whole area from the Harbor/North End to Kenmore Square has things of interest, both within the city or along the Charles River. There are also intersting neighborhoods like Harvard Square and Davis Square, places where yu could while away an hour or two shopping, having a bite, going to an obscure museum, or people watching. The Museum of Fine Arts and the Isabella Stewart Garner Museums are near each other and world class. The Institute of Contemporary Art and the MIT Museums are smaller but well worth visits.

Beaches are more difficult. I would make two suggestions from which to choose: Provincetown on Cape Cod, accessible by fast ferry from Boston, is a tacky town but the Atlantic beaches are fantastic. Crane Beach in Ipswich is only accessible by public transport (train then shuttle) on weekends, but it is one of the most desirable beaches in the northeast because it has sand and is a nature preserve.

A little primer on the waters around Massachusetts: for any place north of Boston, the ocean is significantly colder than Cape Cod and south. This is because the Gulf Stream current comes up from Florida, but veers off towards Iceland once it hits the "elbow" of the Cape at Chatham.

However, having never been to the Great Lakes, I'm not sure but even our cold water might not be too bad for you! Certainly, Manchester-by-the-Sea and Gloucester are good day trips with pretty beaches and other things to do in each town.

Also north of the city accessible by rail are Salem and Rockport - not so much for beaches, but each town would make a good day trip. Similarly, historic Concord, MA, is an easy 1/2 hour train ride and short walk to the town center.

For beaches, you could take the commuter rail south to Hingham, Cohasset, Scituate; or to Kingston or Plymouth. On this MBTA map, the purple lines are commuter rail:
http://www.mbta.com/schedules_and_maps/rail/

You also could take a ferry to Provincetown on the tip of Cape Cod. If you fly to "P-town", the airport is very close to Race Point Beach - but this certainly isn't a place where you'll avoid undertow! Or fly to Hyannis...

Oh, and I meant to add that my mother used to take me on the train to Singing Beach when I was very small; not much undertow there though as MareW said, the waves are small.

On the Cape, the largest waves are on the Atlantic "forearm" in the National Seashore - and definitely go hand-in-hand with significant undertow. The most popular beaches are on Nantucket Sound, with good sand and waves and temperate water. Cape Cod Bay has neither waves nor undertow - and not many beachgoers, either, since the beaches are less desirable on that side. (Two words: black flies!)

Crane Beach is great.

// For a restaurant with both "surf and turf", IMO you really can't go wrong with Union Oyster House. For a place so firmly on the visitor trail, it consistently serves good, classic food.

I think going to Manchester and Singing Beach is a nice day away. Don't know about the waves but it sounds as though it fits your requirements. I don't know what horror stories you've read about Boston and nearby beaches. They are very popular--especially Revere Beach. They're just not as posh as some suburban beaches.

While there are some honky-tonk stores in Provincetown, it is a fascinating fishing/tourist in the summer town with beautiful homes and gardens. A great day trip from Boston.

You could also go out to the Boston Harbor Islands. There is a beach and facilities on Spectacle Island, which you reach from Georges Island. The islands are one of Boston's least known treasures. http://www.bostonharborislands.org/

There are hundreds of restaurants in Boston so it's hard to recommend some without knowing where you're staying, what budget you have for eating, and what kind of food you like or don't like (beyond fish). I have eaten at Mooo and enjoyed my food. It is a nice atmosphere.

In Boston, you'll find that there is good seafood on most menus. So you really don't have to go to a "seafood" restaurant for your husband to get his fish fix.

To say Revere Beach is "not posh" is a huge understatement. It's a beach in a slum.

I'm sure that most of the "horror stories" are greatly exaggerated. I have passed through that area many times without once being wounded by a hail of stray bullets. I love going to the annual sandsculpting festival, and I consider Kelly's Roast Beef to be not only one of my favorite self-indulgent treats, but truly one of the pinnacles of Boston cuisine. Nevertheless, Revere Beach really is not a place where most tourists would want to go.

People don't usually visit Boston for beaches but it looks like you have some good day trip suggestions in the thread. I would only add that you can do some research on the ferries that go to the outer islands in Boston Harbor. You may find some of these have good beaches and the ride is nice.

It is difficult to suggest restaurants without knowing where you are staying but here are a few I like:
Craigie on Main...Chef Maws is terrific
Lala Rokh...Persian in a lovely setting
No.9 Park...overlooks Boston Common

And while I would not call Eastern Standard romantic,it bustles in a good way, the food is bistro fare and the drinks are quite a treat...they take their cocktails very seriously. Plus it's just around the corner from Fenway park...where the magic happens.
Have fun!

I've learned a lot from this thread!

In my opinion, Boston's a truly terrible restaurant town, and in general one will achieve greater success seeking other kinds of recreational activities. But I'll agree with Yurtgrl in endorsing Craigie on Main -- the food is good! Although I have trouble enduring their attitude. I haven't been to Lala Rokh in years, although I used to find it decent and interesting.

Eastern Standard used to be one of the few major cocktail destinations in Boston, but it isn't any more. All of the key personnel have left for other places, and the drinks are now pretty awful. I've forgotten the names of the major players who built the cocktail program at Eastern Standard, but I know that at least one has gone to the bar at Craigie on Main (where the drinks are good), and one has opened an upscale speakeasy-style bar near Eastern Standard called The Hawthorne, in the Hotel Commonwealth (I haven't been there yet).

There are also some excellent bartenders (and some not-so-great ones) at Brick and Mortar in Central Square, which is a spin-off of Drink, which is generally regarded as the premier cocktail spot in Boston. I really like the food at Brick and Mortar too. But it's "small plates" type bar food, and the atmosphere is dark and divey, not fancy or romantic.

If yo are looking for water not to cold I would head for Cape Cod - but the ocean beaches that have large waves have the potential for undertow - I don;t know anyway around that. Just make sure that there is a life guard nearby and don;t swim out farther than you are comfortable. Frankly - I never swim in the ocean - I'll go out as far as the breakers - shoulder high or so - but no further.

And I've never run into jellyfish - either Cape Cod or Long Island - although I suppose it's possible.

There are je;;yfish in the sounds, Nantucket and Long Island. There are no stinging jellyfish, or at least I haven't encounted any while at the beach or shell fishing.

Yes, small clear basically non-stinging jellyfish pretty much every August (and earlier if the waters warm up quickly) in "the sounds" as Ackislander said, plus Buzzards Bay and the warmer waters around NYC. And although not frequent, we definitely get the salad-plate sized harmful man o' war (which technically aren't jellyfish).

IME, undertow is the most dangerous right at the shore, where a strong one can knock a child or unobservant adult off their feet-! We had to learn how to swim to get out of undertow when I was a kid, but these days I'd rather just avoid it!

For seafood, I'd suggest Neptune Oyster or B&G Oysters. Island Creek is supposed to be excellent, but I haven't been there yet. Dolphin Seafood in Cambridge is also very good and for this type of grub reasonably priced. Legal Seafood has several locations and is often very good, though I've had less good luck at the Prudential Center and Kendall Square outposts.

I would also strongly suggest not going to the Union Oyster House, as I've found the food and service there to be of poor quality -- if you must just to say you went there, sit at the bar and stick to raw oysters and a beer. I'm also not a fan of either Barking Crab or Summer Shack.

A couple thoughts on some earlier posts:

--re Revere Beach. You can indeed reach this via public transportation (subway, Blue Line) -- but the beach itself and the water there are not that clean. I definitely wouldn't swim there, myself, nor would I take my shoes off to walk the beach, though you'll see people doing so in summer. And while I'm not so sure I'd want to wander the neighborhood adjoining the beach after dark, I'm not so sure it's a "slum" (for me, that would suggest daytime avoidance as well) -- the neighborhood is gritty but not to my thinking unsafe to walk during daylight. Besides, one can wander the beachfront without having to encounter the surrounding neighborhood. And yes, Kelly's Roast Beef is excellent, and not just for beef sandwiches but also for fried seafood and lobster rolls. You'll have to get the food "to go," though, as there's no seating there -- most people sit in their cars to eat or find a place along the beach walk area to munch. I'll agree that it's not really much of a tourist destination.

--for the most part (Providence and Worcester being the primary exceptions), the commuter rail lines from Boston's South Station are unfortunately not especially useful for sightseeing. The stops along the Greenbush Line past Hingham are not centrally located to the towns they purportedly serve, and it's a long hike to reach anything of interest in these areas. On the Kingston/Plymouth Line, the Plymouth stop is also located a solid (if potential do-able) walk out from the center of town, though there might be a few local buses that connect the two -- plus recent service cuts have eliminated weekend runs on this line as well as Greenbush. The commuter rail lines out of North Station are very useful for tourists, though.

--while it's certainly possible to reach Hyannis or Provincetown via air, it's easy and much more cost-effective to do so from Boston via bus for the former and via fast ferry for the latter. And unlike many Cape Cod beaches, in high season one can readily reach those near Provincetown via trolley service. Wonderful as these beaches are, the water's not warm along them, though -- your best chance of getting halfway warm water at a Cape Cod beach would be at one that sits on Cape Cod Bay.

--maybe I'm just lucky, but I've never encountered black flies at New England beaches -- wooded areas in Northern New England, Western Massachusetts, and Upstate New York, yes. Greenhead flies are another matter, and it's worth checking to see when they're out and avoid traditionally affected beach areas at that time (unfortunately, these include several of the best Massachusetts North Shore ones). Luckily, their season is short, usually only a couple weeks. Both types of flies are brutal, very aggressive and tenacious, with painful bites.

--the whole idea that Boston is a terrible restaurant town isn't one I agree with. It's not in the same league as New York, San Francisco, New Orleans, or Chicago, sure enough, though "terrible" is a different story -- I'd save such an adjective for places like Dover, DE. But that's a long harangue -- maybe another time.

Bachslunch, the greenheads are generally gone from the North Shore by early August. (OP is traveling in mid-August.) At any rate, the two beaches I suggested don't have an issue with them.