Understanding how fish trajectories and passage patterns emerge in rivers is critical to improving the design of waterways infrastructure for sustaining living resources. Decades of work has not yet provided a robust and broadly applicable explanation for fish movement that can operate with such fidelity and accuracy that it can be reliably applied for designing waterways infrastructure, even in cases where consequences are severe for ‘getting it wrong’. Rivers are used in many ways to meet society’s needs. Humans must more rapidly develop methods and solutions to de-conflict the competing needs of society and maintaining fish resources that are valuable commercially, recreationally, and culturally. We analyze a large data set assembled over 20 years with detailed, high-resolution fish movement/passage and water flow field patterns near infrastructure. The 60+ data sets represent eight sites along the west coast of the United States where the movement and passage of juvenile Pacific salmon were measured. While non-salmon species are in increasing need of attention, the inability to develop a high-fidelity and reliable movement hypothesis (computer model) for juvenile salmon – given the tremendous resources over the past 20 years – is not an encouraging sign for reaching a similar goal with other species. Here, we describe a behavior repertoire that may provide encouragement. We explain how water speed, velocity gradient, water acceleration, and pressure may operate, differently, in guiding and repulsing salmon in rivers. We are able to reproduce 2-D/3-D trajectory and passage patterns of salmon in dammed and undammed tidal free-flowing river environments. While more work is needed to fully develop our findings, impending work and data may allow us to demonstrate that the tools we seek for improving society’s infrastructure are possible, allowing us to sustain the fish resources that communities value in their commercial and recreational activities.