In a small marine cave of the Oman coasts in the Gulf of Oman a species new for science,Tethya omanensis(Porifera, Demospongiae), has been found. The cave, Tiwi Sink Hole, shows very peculiar hydrological parameters such as low salinity, high temperature and lack of hydrodynamism. Asomanensisis distinguished in the genusTethyaby uncommon spicular characters, it was suggested that these traits represent a special adaptation of the species to its habitat.