So looking at a map.of New Yorks bays and ignoring depth and bridges I'm going to assume this is about 2 miles long or 10,560ft. I have no evidence and just eyeballed it.
Meaning if you can overcome the skin friction it has a hull speed of about 160mph...without planing.
Modern carriers have a hull speed in the neighborhood of 45mph (though officially the top speed is like 35mph) and normally cruise at 25-30mph so the slow pokes can keep up.
So, as I understand it, a boat (ship) operating in displacement mode is going to be the most efficient, up until that speed. Past that most of the additional power you put in is going into just shoving water out of the way that really doesn't want to, rather than fighting friction. Also it's where the entirety of your ship is trying to climb its own bow wave, so you're trying to push the whole boat up hill.
If you want to go faster than hull speed you need to have a different hull design like a semi-displacement or planing hull. These are a lot less fuel efficient than displacement hulls as well as some other dosadvantages with weight and bad weather, but if you want to go fast they are your only option.
TL;DR: it's sort-of a max speed. It's probably better to describe it as, the speed at which you need to go back to the drawing board for that vehicle.