The assessment of the distribution of marine sponges was conducted in the reef areas of the 21 islands of the Gulf of Mannar Marine National Park (southeastern India). The underwater study, carried out during October-December from 2017 to 2020, included visual observations through random SCUBA diving. Field data for the present study were collected in association with the reef research team of SDMRI during their regular reef monitoring. Small fragments of sponges weighing not more than 5 g were hand-picked or collected using a hammer and chisel in case of encrusting sponges. The collected fragments were immediately transferred to suitable containers and stored in 80% ethanol for further identification and spicule analysis.