 They explored the mouth of the St. Johns River, calling it "la Rivière de Mai" (the River May), then sailed northward and established a settlement called Charlesfort at Port Royal Sound in present-day South Carolina.Spain learned of this French expedition through its spies at ports on the Atlantic coast of France.The Huguenot nobleman René de Laudonnière, who had participated in the expedition, returned to Florida in 1564 with three ships and 300 Huguenot colonists.