The National Marine Park of northern Sporades consists of a handful of small, remote islands and the waters around them. It covers a wide sea area of approximately 2260 km2. These are Alonissos itself, Kyra Panayia, Gioura Psathoura, Piperi, and Skantzoura. Out of these, access to Piperi is forbidden; even boats must keep their distance. The best base to visit the marine park is the island of Alonissos. From there, visitors with their yachts, can explore the whole area.

In the Marine Park there are many animals, such as, dolphins and little whales. The many caves, formed along the coastline of the islets, provide the ideal conditions for the Mediterranean monk seal monachus-monachus to live and reproduce. The geographical location of the area, the ideal climate, the special morphology and the minimum human interruption, make the sea an ideal habitat for many rare species of fauna and flora.