A device and process for measuring tide levels comprising a guide tube having its lower open end immersed below the lowest tide level, a transducer positioned substantially at the upper end of the guide tube for generation and reception of electrical and acoustical signals, a switching circuit for isolating the transmitting and receiving signals, and at least one branch tube provided near the upper portion of the guide tube. The length of the branch tube is determined by a formula that takes into account the wavelength and velocity of the sound signals, and the diameter of the guide tube is determined by a formula that takes into account the wavelength of the sound signals.