CIMSEC – How does one find an object not meant to be found? Forensic maritime investigators in 2017 stumbled across this question when searching for the disappeared ARA San Juan (S-42) – an Argentinian submarine whose mission centered around stealth. Despite the environmental challenges and the restrictions imposed by the profile of submarines, several complementary forensic tools have emerged as authoritative standards and best practices for underwater search operations. These include: (1) optimization of preliminary search boxes through Bayesian probabilities, with updates for posterior probabilities throughout the search; (2) side-scanning sonar systems; and (3) unmanned underwater vehicles (UUVs) for imagery, access, and identity verification. In explaining the efficacies and drawbacks of such methods, this analysis highlights the importance and evolving future of search optimization strategies.