【Abstract】This talk addresses a contemporary event of the sunken Argentinian submarine ARA San Juan S-42 in November 2017. The submarine’s wreckage was found one year later on the seabed off the southern Atlantic coast of Argentina, with its imploded debris scattered on the seabed at the depth of about 900 meters under sea level. But what is implosion? First, we introduce several phenomena of implosions. Then we develop computational mechanics modeling and conduct supercomputer simulations for this study, using the versatile software LS-DYNA as the platform. We first revisit underwater implosion phenomena by the test of pressurizing a plugged aluminum cylinder in a water tank and match the patterns of structural deformations as the important way to validate our computational methodology and model selections. Furthermore, the radiation of the implosion shocks are computed and compared with those in the literature. Using a base model for the submarine, we are able to perform event reconstruction for the underwater implosion of ARA San Juan S-42. Our work can encompass the features of structural fracture and break-up, which were not included in the earlier studies. Furthermore, we show that by adding ring stiffeners (“buckle arrestors”), we can delay the onset of underwater implosion by increasing the tolerance of more water depth for the submarine. All the dynamic nonlinear implosion phenomena can be visualized by video animations obtained from our supercomputer simulations, which are also compared with an artistically rendered video animation. The talk is easy to understand, without specialized prerequisite. Everyone is welcome.