Upon accepting this contract, a red skull will appear on the map in the centre of Cayman Sound, an island to the northwest of our current location. Sail over here and when you arrive, park in the shallow water and swim across to shore.
You’ll notice a green investigate circle in the map. Our target is located within this. Unfortunately the area is swarming with enemies that you will need to avoid if you want to earn that extra 500R. The target himself can be found just to the northwest of the viewpoint. Work your way over to him using the abundance of stalking zones.
When you have identified him, either shoot him from a shrubbery or race out and sprint assassinate him to kill him before any other enemies know you are there. This will fulfil the contract.