The design of an acoustic telemetry system is presented and evaluated. We describe the main characteristics of the communication system, the transmitter and the receiver. The scheme of the proposed design consists of autonomous sensors deployed underwater and networked using acoustics to a central node, which takes advantage of the infrastructure of sea-floor observatories to deliver data in real-time to a land station. The central node consists of a piezoelectric ceramic with custom signal conditioning and processing to demodulate and decode the data acquired by the distributed elements of the underwater network.