Alonissos

Alonissos - swim around a fifth-century shipwreck - is also one of the best dive sites in Greece. Europe’s largest marine park covers some 870sq miles around the northern Sporades island of Alonnisos and its neighbouring 29 islands and islets. Declared a national marine park in 1992, it's home to a colony of around 60 endangered Mediterranean monk seals and three species of dolphin. Of the 400-500 Mediterranean monk seals that remain, approximately two thirds of them inhabit Greek waters. Cuvier’s beaked whales and sperm whales have also been sighted here.

The main town, Patitiri, is located near the island’s southern tip and is the place for organised diving trips. If you hold an advanced open water diving certification, be sure to book one of the limited slots to explore the fifth-century BC wreck off the islet of Peristera. Dubbed the ‘Parthenon of shipwrecks’, this underwater museum has labelled finds and features a mound of 4,000 mostly intact amphorae. Other popular dive sites include the Blue Cave, where you’ll be able to spot coral, sponges, nudibranchs, scorpion fish and groupers.

Location: Aegean Islands, Greece