In a country not noted for ecological foresight, the National Marine Park of Alonnisos (the largest marine park in Europe) is a welcome innovation. Created in 1992, its prime aim has been the protection of the endangered Mediterranean monk seal and several rare seabirds. In summer, licensed boats from Alonnisos and Skopelos conduct excursions through the pristine park. Though it’s unlikely you’ll find the shy monk seal, chances of spotting dolphins are fairly good. Buy excursion tickets from waterfront agencies.
The marine park is divided into two zones, A and B. Alonnisos lies within Zone B, along with the islets of Peristera and Dio Adelphi. Access to Zone A is more restricted, with boats allowed no closer than 400m to most islets. Piperi Islet is protected by a 5km radius due to its importance for monk seal reproduction.