big worm snails, thylacodes arenarius

big worm snails thylacodes arenarius ocean karvner diversity seasnail seawater sea animal aquatic reef diving slovenia istria italy trip travel shell house adria vrsar adriatic vermetidae rovinj holiday exploring gastropod gulf croatia marine seaslug snail mesogastropoda life mollusk slow undersea giant underwater mediterranean fauna nature wildlife water flamingo close closeup creature serpulorbis arenaria