The Sveti Nikola Fort lies at the exit to the Sveti Ante Channel where the River Krka flows into the sea. Surface waters are brackish and abound in schools of fish that live between these two underwater worlds. The crag is overgrown in typical marine organisms – cnidarians, sponges, polychaetes. The seabed is covered in mussels and is home to gurnards scavenging for food and prey. Out of the remains, new life sprouts in the form of fan mussels.