- present participle of careen
Careening a sailing vessel means to beach it at high tide in order, usually, to expose one side or another of the ship's hull for maintenance below the water line when the tide goes out. Small boats, as in the photo, need not always be laid over.
The process could be assisted by securing a top halyard to a fixed object such as a tree or rock to pull the mast over as far as possible. Maintenance might include repairing damage caused by dry rot or cannon shot, tarring the exterior to reduce leakage, or removing biofouling organisms such as barnacles to increase the ship's speed. A particularly well-protected area might be called "Careening Bay" to the locals. Pirates would often careen their ships because they had no access to dry docks. A secluded bay would suffice and this is where they would careen their ships for necessary repairs and/or hull cleaning. This would make the ships faster, and therefore more capable of overtaking prize vessels.
At one extreme of the spectrum was the ancient practice of beaching a ship on a shingle beach with the goal of using wave action and the shingle to scour the hull.
Careening in popular culture
Robert Louis Stevenson's Treasure Island contains a reference to the practice: the Hispaniola is purposely beached on the island. Although the purpose of this is to avoid the uncertainties of anchoring her with nobody aboard, that a piratical crew member would be quick with the suggestion—and the means of freeing the ship later—shows his familiarity with the practice.
careening in Danish: Kølhaling (skibsrengøring)