Of the three types of turtles present in the Adriatic Sea, only one species has been recorded in the Nature Park – the loggerhead sea turtle (Caretta caretta).

The most common species of fish in the bay is saddled seabream, although other fish are also present in a great number of species and specimens. The common ones include: painted comber (Serranus scriba) salema (Sarpa salpa), common two-banded seabream (Diplodus vulgaris), damselfish (Chromis chromis) and Mediterranean rainbow wrasse (Coris julis). 369 fish have been collected and explored through research, and classified into 9 families and 20 species. Based on the collected data it has been established that the shallow bays of this area are significant habitats of juvenile fish. Seahorse (Hippocampus sp.), a species protected by the Nature Protection Act, can also be found in the meadows of algae and sea grass, and it must not be taken from the sea.

The European eel (Anguilla anguilla) has been observed in Mir Lake. It mostly resides at the bottom, under rocks, in mud and cracks. Given that the lake is connected to the sea only through small cracks, it is supposed that the eels enter the lake through the cracks during their larval stage. Their life cycle inside the lake remains unknown.

Through previous research of the underwater world beneath the steep slopes in the area of Grpašćak, around Mir Bay and mala Prisika, corals have been recorded as densely branched colonies of gorgonians, namely the yellow gorgonian (Eunicella cavolini) and the violescent sea-whip (Paramuricea clavata).

The protected red coral (Corallium rubrum) lives in the cracks of the cliffs. The species has become rare because of its slow growth and excessive exploitation.

The bushy coral (Cladocora caespitosa) grows in accumulations in the Telašćica Bay. It is the only coral with the ability to form coral reefs that lives in the Adriatic Sea. It forms bushy communities that grow up to 50 cm. The coral is an endemic species of the Mediterranean.

One of the most interesting underwater inhabitants in Telašćica is the endemic and very rare species of deep-sea carnivorous sponge (Asbestopluma hypogea) found in a cave on the island of Veli Garmenjak at a depth of 24 metres. This species of sponge is associated with deep-sea habitats , and its finding at such a small depth is the second finding of this species in the world. The underlying reason for this is the fact that submerged karst may have ecological properties similar to those of deep-sea habitats, such as insufficient food and light, and a low temperature which together form suitable living conditions for this species of sponge.

Other more significant species of strictly protected sponges are the soft Mediterranean sponge (Axinella cannabina) and the golf ball sponge (Tethya aurantium.)

The underwater world of the Nature Park is home of several protected species of bivalves: noble pen shell (Pinna nobilis), giant tun snail (Tonna galea), and date shell (Lithophaga lithophaga).