I've been on both - though one does wonder what is the difference between them. I've been on a cruise ship, sailed on yachts, and raced sail boats in college. They are both used in the water to carry people and cargo. The picture is of the "HMS" Rose and I was on the ship for this snappy! We we going from London to France back in 1996.
In general - a boat can fit onto a ship but a ship can not fit onto a boat.
A ship needs a crew to run, while most boats may need only one person to run it.
Ships can carry lots of cargo, boats can't really carry much - some maybe a swin suit or two.
Boats tend to manuver quite easily, while ships are another story and may take a tugboat to bring them in.
So is that enough? Per the National Martime Museum the difference is :The Historic Ships Committee have designated a vessel below 40 tons and 40 feet in length as a boat. However, submarines and fishing vessels are always known as boats whatever their size.
Go Figure? Isn't life grand - By the way - either boat or ship - expensive and fun!