The type and composition of freshwater and marine sediments are key factors in environmental research of (a) natural processes such as sediment transport and accumulation, biodiversity, and biogeochemical reactions within sediments and (b) evaluation of source and progress of contamination, as aquatic sediments act as a sink for nonorganic and organic toxic substances. Above certain levels, such substances could harm biological diversity and human health. Geochemical investigations of aquatic sediments in fluvial, lacustrine, estuarine, and marine environments are of fundamental interest for the assessment of natural ecosystems and the level of pollution that potentially harms them. Detailed determination of the chemical constituents of aquatic sediments assists in detecting sources of pollution as sewage, industry, agriculture, abandoned and active mines, landfills, harbor activities, and oil drilling [leakage]. In addition, natural anomalies may indicate mineral resources in a particular region. New methods and approaches for sampling and analysis are continuously being introduced in aquatic sediment research. More attention is given to qualitative and quantitative monitoring of sediment and sediment fluxes, which is regularly established in most European countries and many others worldwide. Unfortunately, uniform legislation of sediment quality [and load] still does not exist on an international level and in most countries does not exist even on the national level. Therefore, more attention should be given to further expansion of sediment monitoring and of establishing criteria for assessing sediment quality and legislative for toxic inorganic and organic pollutants.