Covering the composition and underlying properties of both freshwater and marine systems, this work provides a basis for understanding both. The authors employ a range of examples to explain the behavior of trace constituents in aquatic environments. They cover sample collection and preparation, modern extraction techniques, conservation, and storage. Among a wealth of topics, they delve into the utilization of passive dosimetry, mineralization techniques, speciation analytics, green analytical chemistry, and chemometric techniques. Extensive details on quality control and quality assurance provides a complete perspective on the difficulties of sample preparation in aquatic environments.