Second only to trade in drugs and weapons, environmental crimes are considered the largest illegal business in the world. Although there is no universally agreed definition of “environmental crimes”, this collective term is often understood to describe illegal activities harming the environment and aimed at benefiting individuals, groups or companies through the exploitation of, damage to, trade or theft of natural resources. The root causes of environmental crimes vary greatly, but are mainly due to low risks and high profits in an environment made permissive by poor governance and widespread corruption, minimal budgets allocated to police and prosecution, low employee morale, etc. Unlike any other crime, environmental crimes are aggravated by their impact on the environment and their costs for future generations. In this framework, crimes against water (the so-called “blue gold”) constitute an emerging global issue, and “water crimes” have come to be considered an emerging environmental crime only recently. Environmental crimes may affect water resources in many ways: water may be the environmental resource damaged by a crime (e.g. surface water pollution, or fraudulent water quality reporting); the object of a crime (e.g. drinking water theft); or the means of the crime (e.g. intentional flooding or deliberate poisoning of a water supply). The analysis of “water crimes” is hampered by the fact that offences against water are often recorded under other crimes such as fraud, corruption, trafficking, falsification of documents, terrorism, etc. The main reason for this is the lack of a common definition of “water crimes” and, consequently, the lack of systematic data collection. Starting from the implementation of universal working definitions, the creation of the first inventory on water crimes now makes it possible to place water crimes on an equal footing with environmental crimes that have been always considered of major importance until today. This allowed for a systematic collection of information that is useful for criminological analysis of the phenomenon as well as for assessing, detecting and prosecuting these crimes.