Marovo Lagoon

Marovo Lagoon — Western Province, Solomon Islands

Marovo Lagoon is the largest saltwater lagoon in the world — a double-barrier reef enclosing 700 square kilometres of calm, clear water in the Western Province of the Solomon Islands. It is a UNESCO World Heritage Biosphere Reserve, lightly populated, minimally visited, and diving in a state that is increasingly rare in the Pacific.

The Double Barrier

The lagoon's structure is unusual. A first fringing reef protects the inner lagoon from the open Solomon Sea to the northwest; a second, outer barrier reef separates the lagoon from the open Pacific to the southeast. The water inside is exceptionally clear — visibility typically 20–30 meters — because the twin barriers reduce sediment intrusion and wave action almost entirely.

The Diving

The reef walls — both the inner faces of the outer barrier and the outer faces of the fringing reef — are draped in hard and soft corals in profusion. Nurse sharks rest in the channels. Reef sharks patrol the outer walls. Manta rays cruise the current-swept passages between the inner and outer reefs. The shallow gardens in the lagoon interior are some of the most pristine hard-coral environments in the Pacific, with massive Porites corals that have been growing for centuries.

The undived nature of most of the lagoon means sites are in a state of natural equilibrium rarely seen at more popular destinations. Fish populations haven't been depleted; coral coverage hasn't been damaged by anchor or fin.

The WWII Layer

This being the Solomon Islands, history intersects the marine environment. Several WWII aircraft and small craft litter the lagoon and reef systems — Japanese and American, all heavily colonised with coral growth after 80 years.

Practical Info

• Depth: 5–35m | Difficulty: Beginner to intermediate
• Access: Internal flights from Honiara to Munda (MUA) or Seghe (EGM), then boat transfer
• Best season: May–October (drier, calmer)
• Marine life: Reef sharks, nurse sharks, manta rays, sea turtles, pristine hard and soft coral systems