###### Abstract  
In this paper, the authors present the results of a set of measurements carried out to analyze the transmission capabilities of the LoRaWAN technology for underwater to above water transmission in saline water. A theoretical analysis was used to model the link budget of the radio channel in the considered operative conditions and to estimate the electrical permittivity of salt water. Preliminary measurements were performed in the laboratory at different salinity levels to confirm the application boundaries of the technology, then field tests were conducted in the Venice lagoon. While these test are not focused on demonstrating the usability of LoRaWAN to collect data underwater, the achieved results demonstrate that LoRaWAN transmitters can be used in all those conditions when they are expected to be partially or totally submerged below a thin layer of marine water, in accordance with the prediction of the proposed theoretical model. This achievement paves the way for the deployment of superficial marine sensor networks in the Internet of Underwater Things (IoUT) context, as for the monitoring of bridges, harbor structures, water parameters and water sport athletes and for the realization of high-water or fill-level alarm systems. Internet of Underwater Things; LoRa; LoRaWAN; marine sensor networks; salt water; transmission performance; underwater to above water 2023234726. 20232334726. 20232334726. 20232334726. 20232334726. 20232334726. 20232334726. 20232334726. 2023234726.  
achieved only in Extremely Low Frequency (ELF) and Very Low Frequency (VLF) bands, which feature significant technical limitations preventing the realization of integrated data transmission modules. The most part of portable communication technologies relies on notably higher frequencies, in the Ultra High Frequency (UHF) and Microwave bands: at these frequencies, the implementation of an underwater transmission channel appears to be totally infeasible. Even if a long range underwater radio transmission using standard communication technologies is out of target, the chance to transmit data from limited depths (below 1 m) may be important for a number of applications, in particular, wireless sensor systems in water: some examples include the monitoring of bridges and harbor structures, the acquisition of water parameters or the monitoring of water sport athletes. In all these cases, sensors may be deployed at limited depths, with the chance of transmitting data directly from under water, without the need of installing ad hoc structures to position the transmitting antenna outside the water, possibly at a certain height. With the development of the Internet of Things (IoT) concept, a number of radio technologies have emerged in the last 15 years with the aim of providing efficient data transmission in terms of wide coverage and reduced power consumption. Most of them operate in the unlicensed Industrial, Scientific and Medical (ISM) bands at the frequencies of 433 MHz, 868 MHz and 915 MHz, and exploit a number of techniques to increase the overall transmission efficiency. Among all these technologies, LoRa (acronym of Long Range) [3] has rapidly gained momentum thanks to its excellent features in terms of receiver sensitivity, which allow it to achieve very long transmission ranges at the price of a limited power consumption. Thanks to the Chirp Spread Spectrum (CSS) modulation, receiver sensitivity values up to \(-148\) dBm are achieved, which corresponds to transmission ranges up to some kms in urban centers and some tens of kms in rural areas. Together with LoRa, the MAC layer LoRaWAN (LoRa Wide Area Network) protocol allows the implementation of complex network architectures integrating thousands of nodes. Thanks to its excellent features, LoRaWAN has been identified as an ideal candidate for all those applications where critical environmental conditions limit the operation of other competing technologies.