The paper presents findings from an observation study of medical surgery teams which may be of relevance to petroleum operations. Karl Weick's theory of sensemaking is outlined as a theoretical background. It is argued that prospective sensemaking, i.e. the ability to foresee what will happen during the next seconds, minutes and hours, is essential to efficient and safe collaboration in the operating theatre. Other preconditions for efficient and safe collaboration are recognition of dilemmas and uncertainty. We observed systematic changes of moods and style of collaboration, and suggest that these contributed to efficient and safe collaboration. We further suggest that joking with differences in status and authority helped prepare the surgery team to adapt authority gradients and collaboration style to the demands of the situation.