The AIS (Automatic Identification System) has become one of the most popular maritime communications systems in the world, allowing the data exchange and identification among vessels to avoid collisions at sea. In spite of the uncountable virtues of this system, security and channel saturation challenges have motivated the development of a new version of the AIS, called VDES (VHF Data Exchange System). This system improves the AIS robustness and includes additional services for a wider range of applications. In this paper, a description of the physical layer of the VDES is presented and the most relevant differences between the AIS and VDES are analysed. Moreover, the main challenges that the VDES has to face in the next years are also described and analysed, including a vision about the future applications that will be supported by this system.