Citizen Science is the practice of involving citizens in scientific research by contributing to the increase of scientific knowledge. Citizens around the world can act as scientists by providing important information, which significantly enhances research. Citizen Science projects related to biodiversity and the natural environment have the potential to 1) provide massive data spatiotemporality that can contribute to the rapid and science-based decision-making for the management of natural resources, 2) enhance environmental awareness and the environmental literacy of the participants, through the continuous information they receive and the relationship they cultivate with the natural environment, 3) to provide information that will be used for the creation of problem-solving strategies. For the last 5 years, iSea has been successfully implementing two Citizen Science projects on marine biodiversity, the "Is it Alien to you… Share it!!!" and the "Sharks and Rays in Greece and Cyprus", while now, with the support of the Goulandris Museum of Natural History, iSea manages iNaturalistGR, the "gateway" of Greece to the iNaturalist community, the largest group of naturalists in the world!