Ship adrift
From Chemical Spill Response
If a ship’s propulsion or steering gear fails, the ship is adrift. The movement of the ship is then fully dependent on the movement of the sea (by current and wind).
Any other distress situation can occur to a drifting ship, such as a collision or a grounding, either of which can have serious consequences.
If there are significant waves, and the ship turns sideways in respect to them, it can capsize.
Causes for such a failure could be lack of maintenance or accidental collision. Emergency systems are normally in place to avoid the consequences of such failure and to to resolve them as quickly as possible.