Instream barriers disrupt the critical movements of fish needed to sustain healthy populations. While large dams and weirs attract most attention for connectivity remediation, the majority of barriers are low-head (<3 m) and receive little research or management focus. To tackle these numerous overlooked barriers, we need fishway solutions that are simple, low-cost, and readily deployable at scale. Here, we combine ecology and hydraulic engineering to investigate the potential of a baffled siphon fishway for Australian riverine systems. This design employs flow-reducing baffles inside a siphon, and is intended to be cheap and require little to no mechanical or electrical parts. To trial a range of baffle configurations, we conducted hydraulic and fish behaviour experiments under laboratory conditions using a range of baffle shapes. Using piezometric tappings in a 100 mm diameter pipe, we assessed the head losses specific to each baffle shape and spacings, and to calibrate a 1D hydraulic model. We next ran passage performance trials to examine the behavioural swimming responses of native Australian fish to the different baffles. Finally, we present preliminary results from field trials. Combined, our laboratory and field results provide a fundamental hydraulic and ecological basis for a simple, low-tech fishway design with promise for the many overlooked low-head barriers across Australian rivers.