The growth rate of marine biodiversity knowledge among Indian Ocean countries is not uniform, which is due to the lack and asymmetric growth of human, institutional, and technical capabilities. Biodiversity data in the Middle East marine environments (the Red Sea, the Gulf of Aden, the Arabian Sea, the Gulf of Oman, and the Persian Gulf) are scarce and are generally focused on larger taxa, while groups like sponges, ctenophores, octocorals, polychaetes, and tunicates are poorly known. On the other hand, most of the species diversity information of the region came from coral reef ecosystems, especially from the Red Sea. High maritime activities in the Persian Gulf and the Gulf of Oman as the major waterways for oil and gas transport and the lack of a documented database on total taxa diversity require greater attention for the biodiversity of these environments. Therefore, there is an urgent need to extract, standardize, and evaluate these biodiversity data. To fill a part of the gap, the Iranian National Institute for Oceanography and Atmospheric Science (INIOAS) was officially selected as a regional OBIS node in the Persian Gulf and the Gulf of Oman (PEGO-OBIS) Then, a project (project grant number: 392-011-05) was conducted entitled Gathering, standardization/digitization and interpretation of existing biological data of the Persian Gulf and the Gulf of Oman based on OBIS scheme. the presence Cnidarian occurrence data is part of the above project.