Wang, You-jiangYou-jiangWangYu, LongLongYuAbdel-Maksoud, MoustafaMoustafaAbdel-Maksoud2026-06-052026-06-052026-05-07China Ocean Engineering (in Press): (2026)https://hdl.handle.net/11420/63391Marine propellers are continually expected to achieve higher efficiency, lower noise, compactness, and improved manoeuvrability often simultaneously. However, conventional screw propellers are approaching their performance limits, prompting the exploration of unconventional propeller concepts for further advancement. This paper reviews recent studies on the hydrodynamic performance of several unconventional marine propellers, including tip-loaded propellers, contra-rotating propellers, rim-driven thrusters, vertical axis propellers, tandem propellers, and toroidal propellers. The review summarizes their geometric features, hydrodynamic characteristics, advantages and limitations, underlying mechanisms, and key directions for future research. The findings indicate that: (1) not all unconventional propellers enhance efficiency, yet many offer advantages in noise, vibration, or manoeuvrability; (2) simulation-base optimisation has become the state-of-the-art approach for both design and fair performance comparison among propeller types; (3) tip-loaded and contra-rotating propellers are proven to improve propulsive efficiency, while the newly proposed toroidal propeller requires further scientific investigation; and (4) despite varying levels of technological maturity, research on cavitation, scale effect, and radiated noise remains insufficient for most unconventional propellers.en0890-54872026Springerenergy efficiencyhydrodynamicsmarine propulsionoptimal designunconventional marine propellerTechnology::623: Military Engineering and Marine Engineering::623.8: Naval Architecture; ShipbuildingJournal Article10.1007/s13344-026-0055-8