To provide an alarm, report, monitor and observation system operating at all times principally to observe sea bottom earthquake, to monitor and observe the underwater and water bottom state, to notify a vessel on the ocean of the presence of a rock in the ocean or to notify a sailing vessel of the location of a host vessel for the purpose of prevention of a disaster at sea and development of ocean.

An underwater general monitor A comprising an ultrasonic transmission means 1, an underwater/water bottom monitoring/observing means 2, a power supply means 3 and a fixing means 4 for installing them in the water is installed on the bottom of sea, lake of river. An ultrasonic signal is transmitted constantly toward the water surface and received by a vessel 5 on the water surface equipped with a radio communication unit with a ground station or an ultrasonic receiver 7 mounted on a float 6.