I concur with @Highrisedrifter. Better to be safe than sorry. While no watch is technically waterproof, there are many different ratings used to determine water resistance. Apple Watch is rated IPX7, which means that it's okay for outdoor use but it is not considered a rugged watch that's okay to be submerged in water.
My advice: Feel free to leave your watch on while you're doing dishes or doing anything that may cause a few drops of water to touch your watch but take it off for anything else.