A very basic guide to identifying three different types of water horse.
Kelpies
-Prefer fresh, flowing water (rivers, streams)
-Smaller (14-15 hands tall)
-Solid, common colors (black, gray, chestnut)
-Less aggressive
Each Uisge
-Prefer large bodies of saltwater (saltwater lakes, oceans)
-Larger (16-18 hands tall)
-More color variety, uncommon colors (appaloosa, paint, palomino)
-Very aggressive
Backahast
-Prefers ponds, especially ones covered with plantlife such as water lilies or duckweed
-Usually between 15 and 17 hands tall
-ALWAYS pale (cremello, perlino, gray)
-Easier to approach than kelpies or each uisges, may be playful. (Use caution though, they can still be dangerous)
As always, this is all UPG and you may have different experiences. Also, this is an extremely general guide with a lot of room for overlap. There are totally kelpies who live in ponds, or you may find an each uisge in fresh water for example. Just use your judgement and be discerning.