Stars known to pass directly above an island gave voyagers its latitude. By approaching upwind of an island until its zenith star was overhead, the navigator could then turn due west and run with the wind to his destination . Heading for their fishing grounds at dawn, returning to their roosts at dusk, such seabirds as frigates, terns, and boobies point the direction to their island homes. Fed by warm up drafts from its parent island, cumulus billows thousands of feet skyward and remains stationary, while smaller clouds drift away to sea. Deepwater blue changing to green betrays a familiar reef, enabling the navigator to check his position.
Driftwood hints that land lies to windward, while seaweed indicates an up-current reef.
Light green underside of a cloud heralds the presence of a distant lagoon. Main swell bounces back from an island, and bends around it, creating swell patterns that reveal the island's bearing. Meeting the reflected swell at an angle, the navigator turns into it and proceeds toward his unseen landfall. Birds, cloud formations, and other signs of an unseen island, expand a pinpoint landfall by a radius of 25 to 30 miles. In island groups the circles overlap, forming a screen hundreds of mile wide.