I need 3 restaurant recommendations...
1-seafood restaurant for lunch preferably overlooking the water.
2-romantic Italian restaurant for dinner
3-hangover lunch the next day (ie:cheeseburgers)
Neptune Oyster on Salem Street for Lunch. I can't think of any restaurant on the water in Boston that I would go to on purpose.
Romantic Italian dinner, Mamma Maria's North End
Cheese burger - the Bristol Lounge at the Four Seasons.
63 Salem St Ste 1, Boston, MA 02113
200 Boylston Street, Boston, MA 02116
Waterfront view is a compromise in Boston; there are always better places without a view. So I concur with Neptune as a first choice, but if you need that view, I'd recommend Rowes Wharf Sea Grill at the Boston Harbor Hotel, just a couple of blocks from your hotel. It doesn't suck.
Many options for romantic Italian in Boston. I like the Mamma Maria rec, too: see if you can request the two-person dining room overlooking North Square. It's white tablecloth Northern Italian, a little stuffy and expensive, but reliable. Another option that's a little less formal and pricey is Carmen, also in the North End, a brick-walled enoteca with a more Southern-leaning menu.
Tough to beat The Bristol for a classy hangover brunch, even if the burger is $20. Another option is to cab to the South End, which is brunch central in Boston. A few places there offer fine burgers on their brunch menus (as well as good eye-openers), including Coda Bar & Kitchen, Pops Restaurant, and The Gallows (which does a nice brunch patty melt).
Mamma Maria Restaurant
3 North Sq, Boston, MA 02113
Neptune could fit both 1 and 3. The burger with fried oysters is one of my favorite hangover lunches.