i recall documentaries where USN people refer to an aircraft carrier they are on as a boat.
I assume you’re being tongue-in-cheek. If not, you’ve clearly never seen the Great Lakes. “Lake” is a bit of a misnomer. It would be more descriptive to call them fresh-water inland seas.
There are plenty of ships, and shipwrecks, on the Great Lakes. Considerably more shipwrecks than the Bermuda Triangle.
Google “Ships of the Great Lakes” for more info. 
A relatively high volume of traffic and lots of land to bump into makes for a lot of shipwrecks. The smallest of the Great Lakes, Erie has the most shipwrecks.
The largest (unless you count Michigan and Huron as one lake, which really they are), Superior, is truly an inland sea, roughly 350 miles by 160 miles, with some impressive storms on it, particularly in the late fall and early winter. For example, a mid-sized freighter (650 foot Algoway) that I was working on took waves across the deck, and a few years prior to that another mid-sized freighter (730 foot Edmund Fitzgerald) sank in a storm (possibly from a cargo hatch being blown by the waves, possibly from a shoaling further up lake, possibly structural failure in the pounding . . . ). In a decent blow it is common to have waves thirty to forty feet high and winds of fifty to seventy miles per hour.
No. As an example I offer Peter Griffin’s misunderstanding of poop deck.
They must be ships then.
Another exception to the “rule”: http://www.maritimequest.com/warship_directory/us_navy_pages/destroyers/photos/cole_ddg_67/05_ddg67.JPG
