Submerged laser peening creates powerful bubbles called laser cavitation, which can improve the strength of metal materials. By using laser cavitation peening, researchers can enhance the fatigue strength of 3D metals like titanium alloy, commonly used in aviation and medical fields. The impact from laser cavitation is stronger than traditional laser ablation, leading to work-hardening and compressive stress in the metal. This technique can help overcome the lower fatigue strength of 3D printed metals compared to bulk materials, making them more suitable for various applications.