Automatic ship identification systems (AIS) have much potential to provide useful marine data and inform international marine policies, but inconsistent use of this technology, as well as falsification of data by users, must be addressed, Douglas McCauley et al. emphasize in this Policy Forum. The ocean remains one of the least observed regions of the world, but recently numerous countries and organizations are harnessing the power of AIS, which is enhanced thanks to recent improvements in satellite and computation capability, to fill gaps in ocean observation. AIS transponders publicly broadcast information about a ship's identity, position, and course. This can provide valuable data, for example in monitoring Marine Protected Areas (MPA). Such use has recently shed light on how fishermen responded to MPA closure of Kiribati's Phoenix Island Protected Area. The authors highlight numerous other ways in which AIS data can be useful. Some countries have made it mandatory that vessels carry AIS transponders. Yet, two major weaknesses of AIS remain: only a fraction of vessels are currently required to carry AIS, and some vessels that carry AIS cheat by turning off transponders, falsifying positional data, or transmitting improper identification data. Data analytics can play a major role in correcting AIS noncompliance, the authors note. Newly developed algorithms can process data from thousands of ships to flag events when AIS has been switched off at sea. Other "despoofing" algorithms use diagnostic behaviors to determine the true purpose of misrepresented vessels. Lastly, the authors call for IMO member states and regional fisheries management organizations to begin enforcing proper use of AIS, noting that simply having an AIS unit aboard a vessel, but failing to use it properly, can no longer be viewed as legal compliance.