I'm not in the dream but I saw a dead body being thrown in the dirty tank

I dreamt about a couple has two kids and the kids kept on playing with someone their parents can't see until they saw a dead body inside of their house, at the end of the dream I saw the couple threw away the body on a deep transparent tank with a very dirty water, I kept dreaming that involves water and last time the water is running or like on a top of a dam and now the dream about that dead body on a dirty tank.