A submarine cave near Vrbnik (the island of Krk, Croatia) is 30 m long and has the shape of an irregular triangular prism, with its bottom covered by mud and boulders. Formed in Upper Cretaceous limestone under terrestrial conditions, probably during the Würm glaciation it was submerged during the Holocene rise in the sea-level. Preliminary biocenological studies revealed 23 taxa of macroflora at the cave entrance and 115 taxa of macrofauna (22 Porifera, 7 Cnidaria, 19 Bivalvia, 6 Gastropoda, 1 Cephalopoda, 1 Echiura, 1 Sipuncula, 8 Polychaeta, 15 Crustacea, 6 Bryozoa, 5 Echinodermata, 4 Tunicata, 20 Pisces). Malacostraca comprised 13 species of Decapoda and 2 species of Mysidiacea. Among the fishes only Gammogobius steinitzi is considered to be an exclusive cave inhabitant. The goby Thorogobius ephippiatus is by far the most abundant fish. From the cave entrance and up to 3 m into the cave a precoralligenous aspect of coralligenous biocenosis was registered. The biocenosis of semi-dark caves dominated by Porifera fauna occurs up to 25 m into the cave, while the final 5 m are characterised by biocenosis of caves and ducts in complete darkness with a predominance of Polychaeta.Podmorska špilja kod Vrbnika duga je 30 metara, i ima oblik nepravilne trostrane prizme. Oblikovana je u gornjokrednim vapnenačkim stijenama. Muljeviti i pjeskoviti sedimenti pokrivaju njeno dno. Nastala je u kopnenim uvjetima, tijekom Würma. U holocenu, izdizanjem morske razine špilja je potopljena. Tijekom biocenoloških istraživanja nađene su 23 svojte makroflore i 115 svojti makrofaune (Porifera 22, Cnidaria 7, Bivalvia 19, Gastropoda 6, Cephalopoda 1, Echiura 1, Sipuncula 1, Polychaeta 8, Crustacea 15, Bryozoa 6, Echinodermata 5, Tunicata 4, Pisces 20). Istraživanjem Malacostraca pronađeno je 13 vrsta dekapodnih rakova i 2 vrste mizida. Među zabilježenim ribama, samo se glavoč Gammogobius steinitzi može smatrati isključivim stanovnikom podmorskih špilja. Primjercima najbrojnija vrsta riba u špilji je glavoč Thorogobius ephippiatus. Od ulaza do 3 metra unutar špilje zabilježen je prekoraligenski aspekt koraligenske biocenoze. Biocenoza polutamnih špilja utvrđena je do 25 metara od ulaza, dok je u posljednjih 5 metara razvijena biocenoza potpuno tamnih špilja i prolaza s dominacijom Polychaeta
