The viscous behavior of fluids can be observed in numerous everyday situations. Therefore, it is reasonable to assume that people, since they are usually not specialists in fluids' flow behavior, possess na\"ive conceptions about the viscous behavior of fluids. These conceptions more or less deviate from corresponding scientific explanations. Qualitative studies with preschool children and secondary school students from Germany have already identified various na\"ive conceptions about the viscous behavior of fluids (e.g., that the density or stickiness of a substance explains its viscous behavior). Within the present study, we explore the question of whether similar na\"ive conceptions can also be found among adults around the globe. To this end, based on previous research, an online questionnaire was developed to survey adults worldwide regarding their na\"ive conceptions about the viscous behavior of fluids. The survey was conducted anonymously, online, and voluntarily in spring 2023; participants were recruited via SurveySwap. A total of 406 adults from all regions of the world (primarily Europe and North America) participated in the survey. In this paper, we report and discuss the main findings of this online survey.