Topical inquiries for the Swedish Defence Research Agency (FOI) include analysis of explosive substances in different sample types. Research into explosives in complex matrixes can provide an analytical support function for forensic investigation i.e. tools for areas such as finding bomb factories, identification and risk analysis of home-made explosives (HME) and improvised explosive devices (IED) as well as preventive measures against maliciously intended use of explosives. Additionally, the research may lay the groundwork for indications of health- and environmental hazards. Utilizing state-of-the-art equipment and years of extensive expertise, FOI is able to carry out these types of research tasks to provide security and sustainability for society. The aim of this thesis project is to establish and validate developed methods for collecting, extracting, separating, and detecting trace amounts of explosives in various bodies of water using a solid-phase extraction (SPE) robot and a high-resolution (HR) mass spectrometer (MS) connected to an ultra-high-performance liquid chromatograph (UHPLC). Particular areas of interest include locations in the Stockholm archipelago where experimental detonations of explosives have taken place. Overall, UHPLC-HRMS analysis provides a powerful tool for analyzing explosives in complex matrixes with unambiguous and reliable measurement data. The compounds of investigation were hexogen (RDX), octogen (HMX), pentyl (PETN), and trotyl (TNT). To summarize, during the course of the thesis, trace amounts of some explosives were detected and quantified in various bodies of water. Furthermore, the applied method for the project was successful in qualitatively and quantitatively analyze the compounds of interest with limit of detection ranging between 0.33–11 μg/L (ppb) in various water sources.