Background: Structured water-dance intervention (SWAN) is an aquatic method customized for adults with profound intellectual and multiple disabilities (PIMD). The aims are to describe and discuss how the SWAN program intervention leader, instructors, and support persons (i.e., the staff) co-operate and facilitate interaction with participants with intellectual and multiple disabilities (IMD), and to identify expressions of emotion by the participants during a SWAN. Method: Video recordings of the interactions were analyzed based on dialogical theory and conversation analysis (CA).Results: The analysis showed that SWAN can be described as an institutional activity, on the one hand governed by an overall, pre-planned structure, and on the other hand affected by the moment-by-moment co-operation and interaction between participants and the staff as the intervention is taking place; also, how sev-eral emotional expressions by the participants are responded to by the staff.Conclusions: In interaction during the SWAN, the participants are considered as competent interaction partners, and their multimodal expressions are taken into account by the support persons, instructors, and intervention leader through adapta-tion to the activity.