The surface-piercing propeller (SPP) is used in high- speed planing craft to achieve high speeds. These propellers operate in a semi-submerged state in a two-phase air-water environment. The blades of these propellers are constantly immersed in the water and exit, facing stress and displacement from cyclic load. In this thesis, the fluid-structure interaction (FSI) and crack propagation of the SPP are investigated. FSI study is investigated at four immersion ratios of 30%, 50%, 70% and 90%, under low and high advance coefficients. A coupling of Reynolds-averaged Navier–Stokes equations (RANS) and elasticity theory are used to simulate fluid dynamics and the blade deformation with the multi-physics computational fluid dynamics software STAR-CCM+. The analysis is performed after several rotations of the SPPs at five different positions. The study of crack growth and high cycle fatigue of the surface-piercing propellers (SPPs) are investigated numerically using the finite element method. The cyclic load is calculated from the hydrodynamic pressure on the blade by simulating the fluid around the blade using the computational fluid dynamics software STAR-CCM. The initial cracks are assumed to be created near the blade root and the fatigue life is calculated from the Paris-Erdogan equation. The results show that at the advance coefficient of 0.4, a higher immersion ratio increases torque, thrust, efficiency, maximum stress, and maximum displacement. When the advance coefficient is equal to one, the efficiency, maximum stress, and maximum displacement remain constant for the immersion ratio above 50%. The maximum displacement occurs at the blade tip, while maximum stress is at the trailing edge root. The largest blade deformations happen where the blade enters the water, aligns perpendicularly with the water surface, and exits. The two-phase flow around the blade increases its displacement. The crack growth is followed in 13 steps using the linear elastic fracture mechanic