To investigate the impact of structural parameters of supercavitating projectiles on terminal underwater damage, underwater penetration of three projectiles with different cone lengths was conducted, based on the 12.7 mm supercavitating projectile, against high-strength aluminum alloy curved targets. The Arbitrary Lagrangian-Eulerian (ALE) fluid-structure coupling algorithm was employed and its reliability was validated. Analysis of the simulation results revealed the influence of the cone length on ballistic deflection and the structural response of the projectile-target system during oblique underwater penetration. The findings indicate that projectiles with shorter cone exhibit stronger penetration capabilities, whereas those with longer cone experience greater ballistic deflection upon target penetration. This research provides valuable insights for optimizing the structural design of underwater projectiles and enhancing the anti-penetration performance of underwater cylindrical shells.