The freshwater environment is home to a wide variety of invertebrates, including many larval forms of terrestrial insects. Therefore, many species spend part of their life cycle in or around water. Other species are commonly found on or in freshwater, but are also found away from water.
The key above is part of the Waterbug toolkit, available at https://www.thewaterbug.net/ALT.html
We also highly recommend the associated The Waterbug App. This is a very helpful guide for identifying aquatic invertebrates - including larval insects such as dragonflies and damselflies. The App is free, and available for iOS and Android devices.
This 'Freshwater Invertebrate' category below includes a small number of freshwater crustacea, and various other non-insect invertebrates, such as molluscs and worms.