'Waterproofed' means treated so that water cannot get in. Notice the -ed: it is the past form of the verb 'to waterproof', so it carries the idea that somebody did something to the thing. The boots were not born that way — a coating was put on them. This is the difference between 'waterproof' and 'waterproofed', and it is the whole point of the word. 'Waterproof boots' just tells you the boots keep water out. 'Waterproofed boots' tells you someone made them keep water out. So people say 'a waterproof watch' (it was built that way), but 'a waterproofed jacket' or 'a freshly waterproofed roof' (something was applied to it). If treatment is not the point, use plain 'waterproof' — that is the more common word by far. Most often you meet it in two places. One, as a verb in a sentence: 'We waterproofed the roof last summer.' Two, in a phrase: 'newly waterproofed', 'properly waterproofed'. One honest warning about the whole family of words. In real life, 'waterproof' is used loosely. Companies print 'waterproof' on things that are really only 'water-resistant' — fine in rain, not fine underwater. Careful makers say 'water-resistant' and give a depth or a rating; sellers say 'waterproof' because it sounds better. And a treated coat wears off: a waterproofed jacket needs doing again after enough washes. So the word promises more than the object usually delivers.

（經過）防水處理的。台灣一般講「防水」；若要強調是後來塗上、加工做的防水層，就是 waterproofed，例如屋頂防水工程、外套上防水劑。標示上的 water-resistant 是「生活防水」，等級低於真正的 waterproof。