The Basques were whalers. They started from the coast, using watch towers. Once the Bay of Biscay was depleted they moved further and further into the Atlantic.

Whale meat was mediocre and didn't preserve well, and while whale bone (baleen) is useful enough, but the real target was whale oil, the best lubricant and fuel for lighting.

All of this is from The World the Plague Made: The Black Death and the Rise of Europe by James Belich. (Highly recommended (even to myself – I reread it within a year).