Situation awareness (SA) is generally seen as a mental representation of the system state, an objective measure of the ?situation out there?. In this article, the authors make an argument that SA can only have a meaning in relation to the task of the user and characteristics of the system. This will be argued with the help of a specific environment: vessel traffic monitoring. The long-time constants and the complex constraints imposed on the ship require that the operator monitoring the traffic has a good SA: the operator must make long-term predictions about possible traffic developments. For this, being in control and having SA are inseparable characteristics of the same process.