Fragmentation hazards from underwater munitions remain poorly understood, and no standardised method currently exists to calculate safe standoff distances as a function of depth and charge mass — a critical gap in EOD safety planning.
This study presents a practical methodology for estimating fragmentation ranges and injury hazard zones for underwater explosive charges. A series of controlled small-scale experiments compared cased charges detonated in air and at varying submersion depths, testing three casing configurations to quantify the influence of depth on fragment generation, in-flight behaviour, and size–velocity distributions. High-speed videography and witness panels recorded post-detonation fragmentation; an in-house analysis code computed fragment trajectories and soft-tissue penetration probabilities using established injury-threshold criteria.
Results show a pronounced reduction in fragment count, velocity, and launch angle with increasing depth, producing substantially shorter predicted hazard distances for all submerged configurations. Water depth emerges as a key mitigating parameter: even shallow submersion significantly reduces above-surface injury risk, though fragmentation hazards remain non-negligible for charges in very shallow water.
The findings are discussed in terms of scaling toward full-scale ordnance and implications for operational risk assessment during maritime UXO clearance. Current military procedures lack standardised depth-dependent standoff guidance — this work provides a foundation for addressing that gap.
The Terrorism Risk Assessment, Modelling and Mitigation Seminar Series (TRAMMSS) is a virtual seminar series focused on technical topics related to terrorism risk assessment, and modelling, including blast modelling and response; IEDs; vehicles as weapons; CBRN; big data for risk assessment, security and screening; and associated mitigation measures.
Piotr Nowak is a retired Lieutenant Commander of the Polish Navy with 15 years of operational experience in underwater explosive ordnance disposal. He specialised in developing low-order disposal procedures for high-explosive naval ordnance and commanded the neutralisation of the "Tallboy" bomb in Świnoujście — a 5,400 kg device disposed of by deflagration in an active port, the first operation of its kind in Poland. He holds a Postgraduate Diploma in Crisis Management and is currently a PhD researcher at Poznań University of Technology, where he leads experimental underwater blast research. His work focuses on shallow-water detonation parameters and safe disposal procedures near maritime critical infrastructure. He is an inventor of a patented underwater blast measurement system and consults for the Polish Maritime Office on UXO management in maritime construction projects.
