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Summary
Players earn Doubloons from killing and looting enemy ship crewmembers, from sinking enemy ships, and a variety of other ocean-based activities (such as fishing, nets, etc)
When a player loses their ship (i.e. it is sunk by another player or NPC enemy ship), they will receive a 50% refund of the total amount of Doubloons spent on the ship (which includes registration fees, Doubloons spent on upgrades to the ship, hiring additional crew, etc)
Players sinking another player's ship will receive 10% of the ship's total Doubloon value as a reward