To keep them busy — and out of trouble — 19-century New England whaling captains would engage their crew by providing them whale bones, teeth and baleen, which they etched and created intricate carvings with.

This video by the Mystic Seaport Museum in Mystic, Connecticut, has more: 

Modern scrimshanders use fine dental tools to make their carvings. They acquire their materials legally though estate sales, auctions and antique dealers.