  Context: Requirements elicitation is an essential activity to ensure that
systems provide the necessary functionality to users, and that they are fit for
purpose. In addition to traditional `reductionist' techniques, the use of
observations and ethnography-style techniques have been proposed to identify
requirements. Research Problem: One frequently heard issue with observational
techniques is that they are costly to use, as developers would lose
considerable time to partake, and also depend on luck in identifying
requirements. Very few experience reports exist to evaluate observational
techniques in practice. Results: In this experience report, we draw on several
data sources, covering insights from both developers and users. The data were
collected through 9 interviews with users and developers, and over 80 hours of
observation of prospective users in the maritime domain. We capture `knowns'
and `unknowns' from both developers and users, and highlight the importance of
observational studies. Contribution: While observational techniques are costly
to use, we conclude that essential information is uncovered, which is key for
developers to understand system users and their concerns.
