Seamless transfer of electronic information/data between ship-to-shore and vice versa and between ship-to-ship and shore-to-shore is being developed in the IMO e-Navigation strategy implementation plan (SIP). We have been focused on wireless LAN for ship-to-ship radiocommunication. In a former field radiocommunication trial, omni-directional antennas were used and a few hundred kbps throughput between two ships was measured, which was not enough for our research target (over 1Mbps). In order to get faster throughput, a field radiocommunication trial was carried out again with a few types of directional antennas and RSSI (Received Signal Strength Indication) and the throughput between two ships was measured simultaneously. As a result, multi-path (2-path) model affected by the reflection of the sea surface was confirmed and also the characteristics of the directional antennas such as half-power angle were confirmed, but the measured throughput was fast enough to meet our expectation.