”Fluids” is an interactive and immersive mixed reality art installation that explores the relation of intimacy between reality and virtuality. We live in two different but connected worlds: our physical environment and virtual space. In this paper we discuss how we integrated them by using water and air as interfaces. We also discuss how we designed mechanisms for natural and subtle navigation between and within the different environments of the piece, how we designed the environments and the installation so as to take advantage of the low cost alternatives that are available today.