Moreover, you can tell by the skyscrapers that are in the foreground of the shot, that this ship is freaking huge compared to Enterprise.
I'm guessing it's a long-lost and forgotten colony ship from the earliest days of Starfleet, and the source of both Harrison, and his ire against a Federation that he perceives as having essentially abandoned/forgotten him and his fellow crewmates. A colony ship also pretty much explains the cryo-tubes we see in the ad, and the fact that there's a really big wreck, and presumably at least a few resulting fatalities, pretty much explains the funeral scene we see as well.
The Enterprise was made far bigger in the last movie, in order to fit the dozens of large shuttles, enourmous engineering section and corridor network around and behind the bridge - up from the 289m of the original series to 725m (possibly as big as 1200m!) Although I don't think the ship skimming the water is the Enterprise, it's definitely in the same size range.