Samoa
Swim to the flag: around eighty giant clams, the largest a metre across, wait below.
A hundred metres off Savaia's sand, a flag marks where the village keeps its faisua, the giant clams. Below the surface their mantles ripple in blues, greens and browns, some shells a metre across and decades in the growing. The reef is theirs; you are the visitor, and only ten snorkellers share it at a time.
Savaia established the sanctuary in 2000, when the village decided its stretch of Lefaga lagoon needed protecting; it still runs the site, hires out masks and fins on the beach, and entry stays in village hands. Three species of Tridacna live inside, including Tridacna gigas, the largest of all clams, alongside reef fish and visiting green and hawksbill turtles. Go at high tide, float rather than stand, and keep hands to yourself: a giant clam closes fast, and the coral below is the nursery. It is conservation you can swim through, run entirely by the people who own the reef.
Couple
Drift side by side down the line of clams and pick favourites by mantle pattern; no two run the same colours. The ten-swimmer cap means the lagoon never feels like a queue.
Family
Children who can snorkel calmly get a marine biology lesson with no aquarium glass in the way, and the village briefing sets the rules simply: float, look, never touch. High tide gives the easiest, safest water.
Friends
Swim out together and spread along the sanctuary; someone will surface having found the metre-wide monster, someone else a turtle. Gear hire on the beach means nobody needs to pack fins.
Savaia is day-trip country: carry lunch from Apia, under an hour away, and picnic between swims.
Order oka somewhere on the drive back; the citrus-and-coconut raw fish tastes right after a morning in the lagoon.

Loch Lomond
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Oak-covered islands scatter across the loch where the Highlands begin and the Lowlands end.

Paracas
Peru
Red sand meets turquoise Pacific where sea-lion colonies roar off the desert's edge.

Manuel Antonio
Costa Rica
Capuchins patrol the sand beneath dozing sloths where rainforest walks into the ocean.

Jeju
South Korea
Seventy-year-old haenyeo surface whistling, net bags full, no oxygen but their own.

Apia
Samoa
Samoa's capital wakes to a police band marching the waterfront for the flag-raising.

Saleaula Lava Fields
Samoa
The lava filled a church to its windows yet parted around a single grave.

Matavanu Crater
Samoa
A hand-kept trail climbs to the crater that buried villages; its keeper logs every visitor's country.