Large metal things that float on (or sink in) the really large watery thing.
At some point a boat becomes a ship but naval people are really tight lipped about when this happens. Obviously one of those things that seperates a landlubber from a bluff old sea dog (like the spelling of "separates" :) ).
- -*cough* a boat is a submarine and a ship is a ship *cough* - no, for f**ks sake, it's simple enough: a boat and a submarine are boats and a ship is a ship, but GLEANER is "Her Majesty's Small Motor Launch".
- - so its a rowing ship then? or a life-ship? and mibi you should get that cough looked at. Sounds nasty.
- - Funny man, I'll get your coat then!
- - No need, had it already and the taxi's on it way.
Anything other than a fishing vessel longer than 40 feet is a ship unless it is a submarine. Submarines and fishing vessels are all called boats no matter how big they are.
However, if you are on a fishing boat and a submarine surfaces right in front of you they are called, "Where the fcuk did that b*stard come from?" Hasn't happened much off the West of Scotland since the Antares tried to catch a nuclear sub of her own and went from full ahead to full astern and then (sadly) fully under in seconds - now HM Sub(marine)s always (allegedly) get an escort vessel. Where TF did that B come from can also apply to basking sharks, yachts, tourists washed away on lilos, MOD Plod afloat, fast moving container ships and the skippers fist if you didn't notice any of the above before he managed to say, "Where the fcuk did that b*stard come from?"
Naval Spotters Corner:
Anything small is a boat, as is anything dependent on being carried by something larger - launches, cutters and gigs, for example. Anything without enough space for the Boss to get out of our hair (submarines, mine-sweepers, fishing boats, P2000s, GLEANER) is a boat - it doesn't matter how long. Your yacht is bigger than 40'? - Unless you own Chelsea, it's probably still a boat (owner is not Captain). Once it gets big enough for the Captain to mess "seperately" (deliberate sp error just to keep in the spirit of this), it is a ship. Note that the Captain may still not be senior enough to be allowed to mess separately (or required to invite paying guests to his table on a liner) but that's not the point.
Regardless, the grey and black things are all "Her Majesty's Ship" not "Her Majesty's Boat", unless they are "Her Majesty's Small Motor Launch". GLEANER is HMSML because it has an appointed Captain on the Navy List but isn't big enough for a large sailor to fart in.