Cover them in soy sauce and allow them to soak for several hours. (see note below)*
Cut each piece of bacon in half widthwise.
Wrap each water chestnut in bacon slices and place in a foil baking tray.
Cover the tray in foil and place on the grill over the campfire until the bacon is crisp.
Optional: Serve with toothpicks.
Notes
When I make bacon-wrapped water chestnuts at home, I soak the water chestnuts in soy sauce in a bowl, but when we're camping, I just soak them right in the can.