You can change the water by changing the pre-set tileset to something else, there might be another way too but I dont remember it if so. Though I'd suggest you just download the UTM and start doing terrains with it instead, as Blizzard doodads are so bad I wouldn't even wipe my ass with'em.
And, if you use the UTM, there is a selection of water doodads you can use, with the addition of the best water doodad in existence.
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