Underwater acoustic (UWA) network protocol design is a challenging task due to extremely slow propagation of acoustic waves, low frequency bandwidth and high bit error and frame error rates typically encountered in real UWA environments. In this seminar, I will discuss the design of robust and scalable protocols for UWA networks, focusing on the practical considerations and lessons learnt from multiple lake and sea trials. I will present several protocol designs that integrate a network discovery process, intelligent routing and efficient scheduling via Transmit Delay Allocation MAC (TDA-MAC), to achieve a desired trade-of between network throughput, reliability and energy efficiency in practical UWA network deployments. Based on the results of the lake and sea trials, important conclusions are drawn on the protocol features required to achieve reliable networked communication in realistic UWA environments.