Which sea was crossed by the Polynesian voyagers to settle Hawaii?

The Pacific - and the crossing from the Marquesas or Tahiti to Hawaii is something over 3,000 km of open ocean, against the prevailing wind, to an island group with no landmass anywhere near it, in double-hulled canoes, at least a thousand years ago.

For most of the twentieth century the academic position was that this could not have been deliberate. The prevailing theory held that the islands were settled by accidental drift, canoes blown off course, because nobody could see how navigation without instruments would work. Thor Heyerdahl's Kon-Tiki raft in 1947 was an argument for a different version of the same assumption - that settlement came from South America, downwind, because upwind was impossible.

The demonstration came in 1976. The Hokule'a, a reconstructed voyaging canoe, sailed from Hawaii to Tahiti navigated by Mau Piailug of Satawal, one of the last men holding the tradition, using stars, swell direction, cloud formations and the flight of birds - no compass, no chart, no instruments. He then taught the method to Hawaiians so it would not die with him. Genetics and linguistics have since confirmed the direction of settlement, and the Hokule'a has sailed round the world.