The Nigerian Navy on Wednesday rescued MV Bourbon, a hijacked offshore oil supply ship.
The pirates, however, escaped with two crew members from Russia and Nigeria.
It was the second rescue in a week. On Saturday, the navy recovered an oil tanker in a high seas shootout that killed one of the pirates. Six hijackers were arrested but two got away with two crew members, believed to be from India and Pakistani.
The navy said it rescued the French-owned MV Bourbon on Wednesday, hours after receiving a distress call.
The rescue occurred in the Gulf of Guinea, which in 2013 overtook Somalia to become the world’s most hijack-prone area. The gulf is a major route for shipping oil, which is generally what pirates are after though some kidnap for ransom.