Patent ID: 8208345

Claim:
A personal water safety device, comprising: at least two sonar receivers; at least one water sensing device, each of the at least one water sensing device comprising a sonar sensor communicating with each of the at least two sonar receivers via sound waves, and each of the at least one water sensing device being worn by a swimmer, and operable to measure an elapsed time when the water sensing device is triggered after the swimmer submerges in the water, and transmit the measured time to each of the at least two sonar receivers via the sound waves at regular intervals; and an alarm apparatus wirelessly communicating with each of the at least two sonar receivers, and operable to receive the measured time transmitted from each of the at least two sonar receivers, and generate an alarm upon a condition that the measured time of one of the at least water sensing device exceeds a predetermined time limit; wherein each of the at least one water sensing device comprises: a barrel portion, comprising: a button installed in the barrel portion, and protruding out as a head portion of the barrel portion; and a cylinder connected to the button, water entering the cylinder when the button is pressed; and a base part connected to the barrel portion, the base part comprising a timer connected to the cylinder, and measuring the elapsed time when electrical conductivity of the cylinder is in the predetermined range.