There are cruise ships. And then there is the Queen Mary 2 — an ocean liner, which in the world of big boats, is a big difference from a floating hotel with waterslides and all-you-can-eat buffets. Dramatic video, linked here and from a harrowing crossing seen below, from the North Atlantic shows Cunard’s flagship motoring through reported 40-foot seas, its enormous bow climbing over rolling walls of dark water before plunging into the troughs below. “This is the North Atlantic we came to see,” the video’s caption reads, adding that with the “wind building” and “seas rising,” Queen Mary 2 was “doing exactly what she was built to do.” That last part is important. Queen Mary 2 isn’t technically a conventional cruise ship.…