[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 who would partake, would lose considerable development time. Observation also does not guarantee that all essential requirements are identified, and so luck plays a role. Very few experience reports exist to evaluate observational techniques in practice, and for organizations it is difficult to assess whether observation is a worthwhile activity, given its associated cost. [Results] This report presents experiences from DNV, a global leader providing maritime services who are renewing an information system to support its expert users. 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.