Generally water nationalisation means nationalising the companies which supply water to homes and businesses. Not, er, literally nationalising water as in the substance.
Your koi pond contains rainwater that ran off my roof, down my gutters and through my flowerbed. You owe me £100. Do not pass go.
Your koi pond contains rainwater that ran off my roof, down my gutters and through my flowerbed. You owe me £100. Do not pass go.