The underwater positioning applications with ultra-short baseline (USBL) are based on geographical locating of transponders emitting deterministic waveform from a receiving antenna composed of several acoustic transducers. In addition to be robust against noise and multi-path, the transmitted signal should have low cross-correlation properties for simultaneous positioning of transponders. Costas arrays based on frequency shift keying (MFSK) structure have these characteristics and are commonly used in underwater positioning. In the same time, transmission of non deterministic telemetry data such as immersion which increases positioning accuracy of USBL systems can raise in a multiple access context the level of correlation and false alarm rate of the detector used for positioning purposes. In this paper, a processing chain design combining underwater positioning application and acoustic communication is proposed, discussed, and evaluated for acoustic propagation in pool. The communication algorithm is based on the modulation of binary data on Costas array identifying the transponder. At the receiver, synchronization allowing retrieval of telemetry information takes advantage of correlation process used in USBL processing. Experiments in a pool show that the developed communication scheme can achieve an efficient tradeoff between simultaneous transmission of telemetry data and positioning signal at a limited complexity.