Utilizing Evaporation Duct (ED), a long-range, trans horizon, wireless communication over the sea is explored using experimental measurements and simulations. ISM Band Wi-Fi frequencies such as 5.8 GHz are commonly used to provide offshore wireless communication to marine boats and ships in Malaysia. The range of Wi-Fi is limited due to the height of antenna installed on boats and therefore, the fishermen or commercial users cannot be connected after a certain range. If a signal propagated over the sea is trapped between the sea surface and the ED layer, it can propagate beyond the horizon achieving long-range wireless communication with very less attenuation. Experimental measurements in the ED channel, using 5.8 GHz frequency are performed from 10 km to 80 km path lengths to determine average path loss values. Additional fading, with respect to time, of average mean path loss due to climate-induced ED height variations are determined from the refractivity profile of the ED height variations using simulations. Fade margin required in ED must accommodate this additional slow fading in order to calculate accurate link availability of the wireless communication system. A Link budget using standard Wi-Fi equipment at 5.8 GHz with high gain horn antennas of wide beam width, are used to estimate availability and capacity of the communication link. Results show that using 5.8 GHz frequency, up to 40 km distance with more than 99% link availability at minimum 16 Mbps data rate is achievable.