Hull sinker is a cannon ball which can damage a ship by 20% each round. One hull sinker is shot once in a round and it never misses and once shot, it cannot be returned to the player's hull sinker stock.
To make hull sinkers we will need to gather resources. The resources needed to create a hull sinker need to be decided.
To fire a hull sinker, we need to load the hull sinkers in the ship before attacking. Also hull sinkers can only be loaded into a ship which is not moving. If a previously loaded ship is commanded to move then the hull sinker will return to the player's hull sinker stock. Also, hull sinker damages are permanent and can only be repaired manually. Which means even losing fleets will suffer from hull sinker damage. This is to provide small ships a means to damage bigger ships without the means of voodoo.
Edit
Hull sinker damages are permanent : The ship that has been hit with the hull sinker, its damages made by hull sinker ( not normal cannon balls) are permanent and don't get repaired automatically like normal battles do. So you can hit a strong fleet multiple times and finally win against it. Which is the main idea here. Which means with 5 rounds of attack and each round being started by your ship, you ship can win against any ship. But the only difficulty to get such power is resources and being able to shoot first in every round.
-1 Skyhawk