A proliferation of pirate attacks in the Gulf of Guinea, an expanse of the Atlantic Ocean stretching from Senegal to Angola, is driving a security-boat building boom in South Africa. Paramount Maritime Holdings, a unit of Africa’s biggest privately owned arms-maker, Paramount Group, says it has largely cornered the market for patrol and escort vessels used in the waters offshore Nigeria and neighboring states. The company currently has 26 boats with a total price tag of about $60 million under construction in Cape Town.