Cooling-water intake basins in coastal power plants may experience particle retention and sediment deposition when complex inlet geometry produces large-scale recirculation and low-velocity zones near intake structures. This study examines the use of submerged barriers to mitigate particle retention in a de-identified coastal power-plant intake basin using hydraulic model experiments and hydraulic-model-supported three-dimensional computational fluid dynamics (CFD). A geometrically consistent model-scale configuration, including the inlet channel, main basin, three intake openings, and two outlet passages, was used to preserve site confidentiality while retaining the essential hydraulic mechanisms. Surface-flow patterns, water-depth variations, and sediment-deposition behavior were measured in the physical model and used to assess the numerical model. The numerical results, supported by the available hydraulic-model observations, reproduced the dominant counterclockwise recirculation and a broadly similar retention-prone region. The simulated water depths agreed closely with the measurements, with relative errors below 0.50% for the finest mesh. A water-depth-based grid-sensitivity assessment using 1,221,165; 2,414,216; and 3,378,840 computational cells further showed that the predicted mean water depths remained within 1.15% of the experimental measurements. The assessed numerical model was then applied to examine submerged-barrier configurations installed near the inlet-to-basin transition, with the barrier-performance interpretation limited to the tested mesh, the assumed representative particle condition, and the available qualitative flow/deposition evidence. Under this assumed particle-tracking condition, the original configuration retained 6989 particles at t = 200 s, whereas the 6 cm submerged barrier reduced the retained-particle count to 4956, corresponding to a reduction of approximately 29.1%. In contrast, the 15 cm emergent barrier increased the retained-particle count to 7573 because it blocked overtopping flow and induced new separated low-velocity regions. These results indicate that, among the tested configurations and under the assumed representative particle condition, the 6 cm submerged barrier yielded the lowest retained-particle count, whereas an excessively high barrier may deteriorate the internal flow structure and increase particle accumulation.