In this paper, we exploit cooperative communication for designing an energy-efficient routing algorithm in underwater wireless sensor networks (UWSNs). Each network node is equipped with a single omnidirectional antenna and multiple node coordinates while taking advantage of spatial diversity. This research work is limited in scope to amplify-and-forward (AF) scheme at the relay node and fixed ratio combining (FRC) strategy at the receiver node. The concept of smart environment envisions a world in which various kinds of smart devices collaborate towards a common objective. In this context, smart refers to the ability to acquire and apply knowledge autonomously to achieve this objective, while environment refers to the physical world. Therefore, a smart environment can be defined as one that acquires knowledge of its surroundings, and applying it can improve the experience of its inhabitants.