This guide will tell you how to find Hafid Ship First Mate Cache Key Location in DMZ Warzone 2.
You will first need to go to the port area and get on the Ship, which is in the B6 location on the map. Once you are on the ship, climb the ladder on the ship.
Many Bots are over the ship, so use your sniper rifle to kill most of them. There is another cache to jump on the roof, go down the stairs, and immediately turn right. There, you will find two rooms, and you have to search in both of them. In one of the rooms, you will find the toolbox.