This book summarizes the latest research on cognitive network-layer methods and smart adaptive physical-layer methods in underwater networks. Underwater communication requires extendable and delay-tolerant underwater acoustic networks capable of supporting multiple frequency bands, data rates and transmission ranges. The book also discusses a suitable foreground communication stack for mixed mobile/static networks, a technology that requires adaptive physical layer waveforms and cognitive network strategies with underlying cooperative and non-cooperative robust processes. The goal is to arrive at a universally applicable standard in the area of Underwater Internet-of-Things [ISO/IEC 30140, 30142, 30143].  The book is the second spin-off of the research project RACUN, after the first RACUN-book "Underwater Acoustic Networking Techniques" (https://link.springer.com/book/10.1007/978-3-642-25224-2)