I need help finding a movie?

Okay, so i was really young when i watched this so i forgot the title and the actors in it,.. but it goes like this.... This man i guess takes women to his lake house or what ever and he kills them or knocks them out dresses them in like costumes and chains cinder blocks to their legs gets in a boat and drives to a certain spot in the lake and dumps them and underwater is like a death garden or something does anyone know what im talking about?