A Mystery

........... hubby has been cleaning out the gutters today and I’ve been on ‘ standing at the bottom of the ladder ‘ duty. While I was being a supportive weight to stop the ladder slipping I was looking around ( because I was getting bored ) and I spotted these two full bottles of a clear liquid ( presumably water ) standing in next door’s front garden. They have been there for as long as I can remember ( certainly many years ), in the same position, but the water looked clear and clean and they were both full so presumably had been replenished and replaced in the same spot again recently. But what I can’t begin to fathom out is why .......... any ideas?