Iceland
A young volcanic archipelago off Iceland's south coast offering boat diving among lava walls, sea caverns and drift reefs, shaped by eruptions over the past 10,000-12,000 years including the birth of Surtsey.
Vestmannaeyjar comprises 18 islands plus about 30 rock stacks, formed within the South Iceland volcanic zone over 10,000-12,000 years. The 1963-1967 eruption created the island of Surtsey; the 1973 Eldfell eruption on Heimaey forced an evacuation. Diving is boat-based among volcanic rock formations, shallow grottos, walls and sea caverns; a dry suit is required due to cold water. Source: Wikipedia (Vestmannaeyjar), Magmadive.