Instructions
Get behind one of the crates as soon as the battle begins. Navarro runs to the top deck of the ship and repeatedly fires at you.
Wait for Navarro to fire four shots. After the fourth, he needs to reload. Use this time to come out of cover and kill a few guards. Get back into cover before he fires again.
Kill all the guards to make Navarro flee to the next area. Follow him. In this area, press "Circle" at the prompt to avoid the exploding crates.
Use the same method as the previous area to take out all the enemies. After you do so, a guard holding a grenade launcher appears. Take him out and Navarro runs up the stairs.
Follow Navarro upstairs and hide behind the crate closest to you. Wait for Navarro to stop shooting. When he does, roll from this crate to the next one. Repeat this until you are close to Navarro.
Run up to Navarro and press "Square" to initiate a quick-time event. You must press the buttons shown on the screen to kill Navarro. When Navarro is defeated, you have won the game.