Underwater sensor networks (USNs) promise innovative and exciting applications, viz. oceanographic data collection, environment monitoring, exploration, and tactical surveillance. Underwater wireless sensor networks (UWSNs) though pose significant research challenges due to the harsh underwater environment. In UWSNs, acoustic is thought to be the only viable means of communication. Underwater wireless acoustic sensor networks (UW-ASNs) present a wireless channel with key challenges, specifically in shallow oceans such as long propagation delays, signal attenuation, man-made and ambient noise, low bandwidth and high transmission energy. We propose a new paradigm for UWSNs, namely underwater wireless hybrid sensor networks (UW-HSNs), which introduce the concept of hybrid communication. UW-HSNs combine the best of both worlds, i.e., the practicality of underwater acoustics and the high-performance of radio communication. The basic idea is to use radio communication for large and/or sustained traffic and traditional acoustic methods for small data volume. Furthermore, we introduce TurtleNet, an architecture based-on UW-HSNs concept, and we propose an asynchronous and distributed routing protocol for TurtleNet. Based on the nodepsilas state, the protocol decides which communication channel to utilize. TurtleNet is simulated using the ns-2 simulator. Simulation results reveal the promising performance for TurtleNet, and hence validate the UW-HSNs concept.