Acoustic underwater tags are key devices to study marine animals and comprehend their patterns, which provide essential behavioural information for applying new conservation policies. At present, all the acoustic tags have a unidirectional communication protocol, which introduces important limitations for their localisation such as range measurement, and in situ reconfiguration. To solve these issues and improve the current state-of-the-art acoustic tags, a new bidirectional tag device is presented in this paper. This innovative tag will allow new studies and will open a wide tracking capability by using autonomous underwater vehicles and range-based algorithms. Here, the main architecture of the tag, and its characteristics are presented alongside the first laboratory tests, and the results obtained.