Leading-edge tubercles have been investigating widely on the performance of foils in the last decade. In this study, the biomimetic tubercle design has been applied to the corner shape on a deep-draft semi-submersible. A numerical study on flow over a deep-draft semi-submersible (DDS) with a biomimetic tubercle corner shape was carried out to investigate the corner shape effects on the overall hydrodynamics and motion responses. The hydrodynamic performance of the biomimetic tubercle corner is compared with a traditional round corner design platform. It is demonstrated that, as the corner shape design changed, the motion responses alter drastically. In addition, the flow patterns were examined to reveal some insights into fluid physics due to the biomimetic tubercle corner design. The comprehensive numerical results showed that the three-dimensional effect, which causes spanwise flow, can be reduced by a continuous spanwise (column-wise) variation of the shear-layer separation points.