Navigators From The Marshall Islands Used Wave Charts To Guide Their Way

For the untrained eye, the sea only looks like a featureless expanse of water. But for master navigators of Oceania, the sea is full of signs and clues that could help them reach their destination — from driftwood, birds, and even the direction of the waves.
Navigators from the Marshall Islands use wave charts to travel through the small islands and atolls in the region. These charts, which capture the distinctive patterns of ocean swells, are a result of constant observation of the sea from land. But as these are not maps, they are not brought to sea. Instead, the sailors memorize these stick charts.
Wave charts have three types: the rebbelib, which show whole island chains; meddo, which represent ocean swell patterns in small areas; and mattang, which teach basic interactions between land and sea.
The wave charts have been a crucial element in making the Pacific Ocean trade routes possible. These routes stretched "at some points all the way from New Zealand to South America." Now that's bonkers!