Background <p>This work investigates the implosion behavior of 3D-printed metallic cylinders, focusing on structural configurations traditionally used to improve collapse resistance. Additive manufacturing (AM) enables the creation of complex geometries that are difficult to fabricate conventionally, offering opportunities to optimize underwater pressure vessels for specific environments.</p> Objective <p>This work focuses on experimentally characterizing the implosion behavior of metallic 3D-printed cylinders and enhancing the collapse pressure while adding little weight. To this end, three cylindrical geometries were designed and tested: single-hull, single-hull with internal stiffeners, and double-hull with a combination of internal stiffeners and filler materials.</p> Methods <p>Numerical models were used to predict collapse pressures and modes. Cylinders were printed using 17–4 PH stainless steel and imploded. For the double-hull structures, foam and polyaspartic fillers were also used to evaluate their influence on structural performance. Implosion behavior was recorded using high-speed imaging and dynamic pressure sensors, and deformation was analyzed using 3D Digital Image Correlation (DIC).</p> Results <p>Results show that print quality strongly influences collapse behavior, with manufacturing variability leading to significant performance differences. Implosion failures were initiated due to both instability and material failure. The influence of stiffeners and filler materials on collapse resistance was quantified. Post-mortem inspection revealed extensive fracturing during implosion.</p> Conclusions <p>These findings demonstrate the value of 3D printing in producing lightweight, functional pressure vessels tailored to underwater applications while discussing potential limitations.</p>