The Automatic Identification System (AIS) tracks vessel movement by means of electronic exchange of navigation data between vessels, with onboard transceiver, terrestrial and/or satellite base stations. The gathered data contains a wealth of information useful for maritime safety, security and efficiency. This paper surveys AIS data sources and relevant aspects of navigation in which such data is or could be exploited for safety of seafaring, namely traffic anomaly detection, route estimation, collision prediction and path planning.• Real time anomaly detection can identify potential se-1 Operating costs usually include crew, stores and lubes, maintenance and repair, insurance costs and overhead costs and are often distinguished from voyage costs such as fuel and bunkering cost.2 It should be mentioned that there are also other types of data (such as radar, video etc.) that can be used for these applications, but their corresponding algorithms and mechanisms are quite different from that of AIS based and thus are out of the scope of this paper.