The Institute for Defense Analyses (IDA) is a not-for-profit company that operates three Federal Funded Research and Development Centers (FFRDCs). We perform scientific and technical analyses for the US government on issues related to national security. Recently, we performed a numerical analysis for the Strategic Environmental Research and Development Program (SERDP) to explore the fidelity of computational models for predicting the initial penetration depth of Unexploded Ordnance (UXO) in underwater sites. This briefing provides a summary of our analysis. A separate, longer briefing describes the details of our analysis.