The underwater positioning applications with ultra- short base line (USBL) antenna have expanded significantly over last decades. Their principles are based on the geographical positioning of transponders emitting deterministic waveform (Costas arrays) from a receiving antenna composed of several acoustic transducers. Recovering from the transponder of external information such as immersion can increase accuracy of USBL positioning system. However, to transmit telemetry data, the processing chain chosen should have some characteristics. Robustness of environmental conditions (noise, multipath ...), maintaining of positioning performances (simultaneous transponder positioning) and low battery consumption (immersed autonomous transmitter) are some of the main constraints apply to the processing chain. In this paper, a processing chain design combining underwater acoustic communication and positioning through BFSK modulation of the data over Costas arrays is proposed, discussed and evaluated. Results show that the developed communication method is an efficient tradeoff between simultaneous transmission of telemetry data and positioning signal at a limited complexity. An experiment at sea will be conducted by IXSEA soon to confirm these first lab results.