Follow the marked targets and take them out. Be careful of the enemy SAM sites on the islands and enemy helicopters. After destroying the gunboats, head to the next location and destroy the military patrol boats attacking the rebel gunboat. Destroy them all. There’s also a nearby military outpost so might as well liberate it by destroy all chaos objects. (Guardia Massos II)
Next, get to the gunboat and carefully steer through the seamines until you reach the target location. Get off the boat for a quick cutscene. Get back to the boat and go to the next marker. Steer through a sea mine field again and stick around a bit to destroy the enemy patrol boats. You can ram the smaller ones and use nitrous to jump over the larger gunboats. Once clear, disembark and check out the contacts.
Return to the boat and follow the path to the final informant. After the cutscene, you’ll have to defend the location from the enemies. Deal with the patrol boats first, then hijack the helicopter and take out more enemies. Reinforcements will arrive via land vehicles behind your allies so engage and clear them as well. Finally, a heavy gunboat will appear. It will be a tough nut to crack but continue attacking it until the mission objective is completed. After reaching the cove and the cutscene, you’re free to explore and liberate this new province again.