Most likely it's a cargo ship. That far out though there's too much haze, so you're not going to make out any detail. There's a lot of busy ports
on the East Coast, so seeing them isn't that unusal. When I used to live in the Chesapeake Bay area, I'd see ships coming and going all the time.
BTW, just looking at the Maersk ships, you'll also see they come in all shapes and sizes...
www.google.com...
Could also be a Navy tender or Merchant Marine even (which are pretty much the same as commercial shipping vessels), but because of the distance
you're not going to see the hull markings.