Mother ship must be able to know accident occurrence information rapidly to rescue crew who fall in sea. In this paper, designed and manufactured transceiver of prescribed 447 MHz is operating as low power radio station specified in Radio Regulation. So, it is available without special permission proceedings getting form probation so that the use of this system may be easy. the system has been started for operation when the sensor get in touch with water. The system transmits with modulation by 500Hz square wave, and the receiver alarms when the transmitted signal is received. Therefore, the system can be used for not only saving a life, but also for low speed of data transmission below 2,400 bps, and other purposes.