Essentially, the IoUTs includes underwater sensors, autonomous underwater/surface vehicles, base/master stations, buoys and ships, and has become an important part of the evolution of smart oceans in smart cities. This is not limited to the several attempts and references in [5; 6] to emphasize the importance of IoUTs, as most underwater areas remain unexplored (only 5% of underwater volume has been explored). To the best understanding of underwater, Figure 1 presents the scenario of the underwater environment. In any underwater scenario taken from [2], the process of localization is important. Basically, localization is a key activity that detects a target's location underwater for different reasons such as data classification, tracking nodes underwater, and coordinating the movement of node groups. This is because the sensor data is meaningful only when sensing nodes are localized [7]. In underwater communication scenarios, the nodes that have ther \"location information' called _'beacon or anchor node'_ that generate \"_beacon message_\" to broadcast to other nodes for communication. The beacon node is a communication gateway capable of building an underwater network and pursuing the localization process [8; 9]. The process of localization enables underwater communication, sensing and control of the whole network's topology. All existing techniques based on base station localization, but some or few research papers discussed the idea of localization through 'beacon node'. There is dire need to understand the difference between base station and 'Beacon Node Localization (BNL)', which is quite interesting. This BNL has enough potential to expand the horizons of research. The beacon node is responsible for the formation of underwater networks li same as the base station. Several important decisions are based on BNL; for example, computation complexity, distance of neighboring node, network strength, receiving signal strength, angle of arrival and its difference, time difference of arrival and reliability analysis, etc. [10]. Most importantly, the beacon node is fully responsible for localization based on the previously mentioned parameters. Effective strategies and reliable shield embedded beacon nodes ensure localized sensor nodes at various places with minimum margin of cost and maximum location-oriented indication of neighboring node list (that need to be localized). The efficient localized nodes and its reliability challenges are another crucial issue in underwater scenarios. Most of the localized nodes cannot be considered secured after localization  
Figure 1: Underwater acoustic sensor network: a scenario [2]. due to unreliability factors, data handling, estimation errors, blindly selected localized nodes, unexpected changes in underwater environment, dynamic uncontrolled network topology, node behavior regarding joining/leaving the network boundaries, etc. [11]. Recently, BC-based distributed, decentralized, peer-to-peer networks have evolved to enable the safe and cost-effective storage of underwater IoT data without depending on any intermediate trusted authority, while maintaining anonymity [12]. BC can support decentralization for capturing IoUTs communication processes as well as secure processing and exchanges data with other organizations. Decentralized access control and distributed trust are required for almost all IoUTs applications. Indeed, even with the bulk of the research found on BC-based localization in WSNs, the same development of BC in the undersea sector has yet to begin. Present underwater communication emphasizes the adoption of BC localization algorithm that can calculate and secure the unknown node's location, authentic accuracy and improve its efficiency, particularly when the environment is unmanned and hostile. In this research, a trust-based hybrid beacon node localization (THBNL) communication framework is proposed for underwater problems regarding BNL.