>
But if you say that a battleship floats on the water in a similar way to a rubber duck floating in the water... it's actually not similar... they are the same. It's the same water and the same physics. The "only" appreciable difference is scale.But battleship doesn't equal floating in water, floating in water is a property it has.
If you're saying "the way a battleship floats in water is like how a rubber duck floats in water" then it's not an analogy, it's as you say just describing two versions of the same thing.
But it is an analogy to directly compare the two objects, because "floating on water" is a property of the objects it's not the object you are comparing.
Wikipedia begins its page on analogies with this, sourced from The Oxford Companion to the English Language: "Analogy is a comparison or correspondence between two things (or two groups of things) because of a third element that they are considered to share."
Or Marriam-Webster: "a comparison of two otherwise unlike things based on resemblance of a particular aspect"
Apart from rubber ducks and battleships both having the "third element", or aspect, of "primarily used for floating on water", they are definitely two
completely different things. Nobody could look at a rubber duck next to a warship and say "they seem to be the same thing".
The more closely related two things are the more useful and less stretched the analogy available, which is why the analogy about radio waves was so enlightening to so many people in this thread. But it's bang on as the definition of what an analogy is.