This document aims to introduce project participants to Citizen Science (CS) and to assist them with selection of CSi activities, based on certain criteria, which are relevant to lakes and that support the Mission Ocean & Waters goals. We first explain the meaning, importance and usefulness of the CS concept in lakes and then provide the methodology used to create a catalogue of existing CS schemes, and the data post processing. We conclude with some suggested schemes for each Mission aim. This is meant to give the readers a good understanding of the catalogue and of the proposed guidelines for detailing, selecting and designing CS schemes depending on general parameters and local contexts (i.e., availability of resources and volunteers’ maturity level).