Chico is mostly invulnerable but he seemed to take damage once or twice. So I gave him gold armour and a good sword, the same as I give to all my officers. Then...Now you've got me curious!
Towards the end of the story, you encounter Bartolomeu o Portugues, and have the option of either killing him (as the Vice Admiral wants) or joining him. If you join him, you lose contact with both your ship and Chico Cois.
Later on, after you've made your peace with the governor at Kralendijk, your old ship shows up, now under the command of Chico Cois, who's supposed to kill you. You fight him on the ship's deck. He's not invulnerable any more but he was still carrying the gold armour and good sword I'd given him earlier, so most of my hits didn't do him any harm. Of course, I was also carrying gold armour and a good sword. So I eventually won, but it was the sort of long drawn-out duel which is usually the climax to any good swash-buckling film.
Later on, after you've made your peace with the governor at Kralendijk, your old ship shows up, now under the command of Chico Cois, who's supposed to kill you. You fight him on the ship's deck. He's not invulnerable any more but he was still carrying the gold armour and good sword I'd given him earlier, so most of my hits didn't do him any harm. Of course, I was also carrying gold armour and a good sword. So I eventually won, but it was the sort of long drawn-out duel which is usually the climax to any good swash-buckling film.