Transportation planners occasionally notice a curious lack of consistency and communication between hydrologists, fisheries biologists and wildlife biologists regarding passages designed for their respective specialties. Several substantial differences in treatments between aquatic and terrestrial passages at highways masks the majority of similarities. At one end of the continuum, aquatics passages can be characterized by a total containment within a watercourse, with no need for modification of the shape or size of water conveyance structure as long as the structure maintains hydrological functionality. At the opposite end of the continuum terrestrial passages can be intentionally designed to avoid water conveyance entirely. Between these two extremes lie similarities in the need for functional streamcourses that allow passage for all age classes of fish and wildlife, as well as high water events. Our paper discusses the common mistakes made when considering only one passage category and suggests remedies designed to integrate the needs of terrestrial and aquatic organism passages. Our paper also discusses the professional basis for the occasional forgetfulness in dealing with other disciplines using lessons learned on this topic by the USDA Forest Service as an interdisciplinary land management agency.