Estimates of bed stability in coastal environments are essential to physical, biological, and chemical investigations of cohesive sediments. The Core Mini Flume (CMF), a 200 mm diameter annular flume has been designed to undertake sediment stability experiments on collected intact sediment box cores. Bed properties were assessed for replicate box cores at 3 contrasting sites in UK coastal waters (Tyne [in 2011 and 2012], Plymouth and Celtic Deep), each covering a maximum area of 80 m2. No significant horizontal spatial variations were found for grain size, bulk density, porosity, or oxygen penetration at the sites. Resuspension experiments performed on replicate cores yielded highly replicable results for each site, giving average erosion thresholds of 0.33 ± 0.02 (Tyne 2011), 0.215 ± 0.03 (Tyne 2012), 0.23 ± 0.01 (Plymouth), and 0.09 ± 0.006 (Celtic Deep) Pa and erosion depths of 10.7 ± 1.7, 6.63 ± 1.10, 3.65 ± 0.95, and 4.6 ± 0.5 mm. Using an already established methodology, the CMF allowed detailed replicate experiments to be performed on-board ship rapidly after sediment collection, while minimizing the time spent at each station. The use of intact box cores minimized the disturbance to the bed often associated with recovering material to a laboratory or remoulding a bed. We have demonstrated that the convenience of laboratory-based methodologies can be combined with the benefit of prompt investigations on undisturbed beds complete with overlying in situ water to produce robust measurements of sediment stability.