25 years afloat since 1954? I would have figured it was floating the whole time. Turns out, they get the 1954 date from the opening of their first restaurant, "Anthony's," (not related to Anthony's on Middle Street) which was not floating since it was on Fore Street. I think their sign is a little misleading and should maybe instead read: Dimillo's Floating Restaurant, open under various names and locations since 1954 and floating since 1982. That is a mouthful though, so probably best to keep it like it is.
An informative history and the full menu of DiMillo's can be found here. And no, I'm not being paid by DiMillo's (but I wouldn't mind if I was) and will yes I will post a photo of mine when I get home.