Wireless sensor and actor networks (WSAN) are composed of low-powered, low-resourced, densely deployed sensor nodes and high-powered, resource-rich, sparsely deployed actor nodes to perform distributed sensing and acting tasks, respectively. Sensor nodes sense the physical phenomenon and report to actor nodes at earliest possible time for appropriate action by the actor nodes. The major objective of WSAN is to have the desired action correspondent to the reported event with higher precession. Due to the coexistence of sensor and actor nodes, one of the major challenges in such networks is communication and coordination mechanisms among the sensor and actor nodes. We have considered the problem of communication and coordination and proposed an efficient model based on geometric structure called Voronoi diagram. Our protocol is based on clustering (virtual grid) and Voronoi region concept. Simulation results demonstrate that the proposed protocol outperforms in terms of throughput, packet delivery ratio, average delay, and normalized routing overhead.