At 6 knots I’m 95% sure they were just some fisherman wanting to trade fish
and cigarettes, or even just out of plain boredom wanting to meet some foreigners. Or as Mark said, running drift nets …. Picket boats often chase after you to make sure you don’t turn into their nets.
Better tactic is to make a dramatic course change away from them at the beginning (50-60 degrees) to show you’re not interested. VHF
radio outside developed areas doesn’t usually work due to language problems.
Your early 10 degree changes were small enough to mean nothing to them and they just kept adjusting until they realized you were not interested.
we get that all the time and in good visibility I usually just make a jog to create a safe distance then return to course.
It is sad that it has become difficult to trust the local fishermen when meeting in open sea.
They used to be a great source of fresh fish
and a friendly encounter with a fellow mariner and still are if you can protect yourself.