This paper presents studies, carried out by Télécom Bretagne, concerning new radio technologies (mainly WiMAX, 802.16e) in the maritime environment. The aim of these studies is to reinforce the quality and the robustness of such transmissions. Several measurements were set up to characterize the propagation channel in maritime environment in order to study the communication performances of WiMAX. This characterization was obtained by specific experimental devices, developed and implemented by Télécom Bretagne. The experimentations were carried out at frequencies of 3.5 GHz (Licensed WiMAX Band in France) and 5.8 GHz (Free Band in France). Similar studies [1] and [2] were already carried out, but they did not take into account all the environment characteristics, namely tides and coast relief masking. Our study looks at these parameters for a better understanding of the propagation in operational transmission environments. In this paper, measurements were carried out by measuring the mean received power both for several distances over the sea and for a coastal point-to-point link during long periods. Part of the work presented in this paper has been obtained during the Ex'treme project.