Sea Trucks Group said in a statement Friday that one other sailor remained missing from the sinking of the tug boat Jascon 4 some 14 nautical miles off the coast of Escravos, Nigeria.
The company says the boat overturned Sunday while trying to tow a tanker in the area.
The company says it has halted recovery efforts as the ship is now too unstable for divers to work in.
Offshore work can be dangerous, as sailors face Nigeria pirate and militant attacks. Industrial accidents happen as well. A sailor drowned in 2010 after falling overboard from a boat working for French oil firm Total SA.