CAPTAIN: A Data Collection algorithm for underwater opticalAcoustic sensor networks Abstract   Underwater sensor networks are used to collect data from aquatic environments. Nodes from these networks usually communicate via acoustic or optical transmissions due to the poor performance of radiofrequency communication in these environments. Acoustic transmissions achieve longer distances than optical ones, but also consume more energy and have lower bandwidth. Underwater opticalacoustic sensor networks (UOASNs) combine both types of communication to explore the best of each one. In this paper, we propose CAPTAIN, an algorithm to perform data collection with data aggregation in UOASNs. CAPTAIN divides the network into clusters, builds a routing tree, and uses data aggregation to deliver all data collected to the sink node. Experiments showed that, compared to the shortest path algorithm, CAPTAIN led to lower network energy consumption, especially in denser networks, where it was able to consume, on average, up to 73% less. CAPTAIN could also achieve lower average latencies (up to almost 83% lower) and higher rates of data collected per hour by the sink node using fewer acoustic transmissions in clustered networks.

PCon: A Novel Opportunistic Routing Protocol for DutyCycled Internet of Underwater Things Internet of Underwater Things (IoUTs) has emerged as an evolution of traditional underwater wireless sensor networks, with programmable nodes interconnected to the Internet. Despite the advancements, IoUTs will still face critical challenges imposed by the use of the lossy and energyhungry underwater acoustic channel. Two major critical challenges faced by IoUT applications are the low reliable data delivery due to the poor quality of underwater acoustic links, and the high energy cost for underwater wireless communication. In this paper, we tackle both challenges by proposing the PCon protocol. The PCon is a powercontrolled opportunistic routing protocol for data routing in dutycycled IoUTs. At each hop, the PCon protocol selects the most suitable transmission power, from a set of discrete transmission power levels, to maintain a reasonable data delivery ratio while reducing the energy consumption of dutycycled IoUTs. To do so, the PCon takes into consideration the energy cost for delivering the data packet, calculated as a function if the probability of having the nexthop node awake during the transmission. Simulation results showed that the PCon protocol, even in a harsh scenario of dutycycling of 50%, ensures a packet delivery rate of 40% while decreases the energy cost in 78%.