This trick requires a decent amount of hull armor and 10 or more mortar rounds for the Jackdaw ship. Travel to the legendary ship battle in the northeast corner of the map, with the two legendary ships that attack you. You will not be able to defeat both ships without your ship fully upgraded, but you will be able to defeat one if you complete the following steps. When the battle starts, shoot two mortar rounds at the ship you are focusing on while turning around, then release your fire barrels. When they get close, use your heavy shot. Do not get between the two opposing ships or you will quickly be defeated. Once they pass, keep shooting mortars at the ship you are trying to defeat while they are turning around. Repeat the previous steps until you destroy the ship you are focused on. Quickly pick up the loot from the destroyed legendary ship, or else the other ship will ram and sink you quickly. You will get 10,000 Reales and be able to keep it after you die. Repeat this process as many times as desired.

Note: This trick requires the cannon and/or shot upgrades; or upgrades to your chain shot and ram abilities. Also, the Brothers-In-Arms must not have been sunk yet. Start a battle with a group of ships, then sink one of them and ignore the other ships. Collect your loot, then intentionally fail. After respawning, the ship you sunk will also be back with its loot, and you will still have your previously collected loot. Repeat this process as many times as desired to earn 10,000 Reales each time.