"Sir, we're going to handcuff you," a coast guard from Sao Tome tells a man accused of fishing illegally in the archipelago's waters.
But the "fisherman" is really a French navy seaman disguised in a T-shirt, cap and sunglasses -- a member of an unusual multinational training exercise to combat crime in the Gulf of Guinea.
Illegal fishing, piracy and hostage-taking haunt the vast bay lying off West Africa, whose coastline runs from Liberia in the west to Gabon in the south.
According to the European Union, the Gulf of Guinea is the "worst-affected region" in the world for unauthorised fishing. In 2016, around a third of all catches, a haul worth about 1.5 billion euros ($1.8 billion), were illegal, it says.
In a survey of sea piracy in 2017, the International Maritime Bureau found that of 16 incidents around the world when a vessel came under fire, seven occurred in the Gulf.