Maritime communication has been considered as a core issue in the marine activities. However, insufficient knowledge of radio channel characteristics over the sea limits the development of wide-band wireless communication systems for maritime applications. In order to increase understanding of the radio channel over the sea, the modeling of wireless between the UAV and vessels is studied. In this work, a channel-modeling effort using the finite-difference time domain method (FDTD) is conducted to assess the effects of sea surface conditions on the marine communications. Data analysis conducted on the receiving waveform of many receiving points over the sea has produced the path loss characteristic.