Purpose:
After putting together the mod for the ghost galleon, I was asked to do something similar for the submarine.

Changes:
This boosts the submarine to the following stats:

Hull Health: 150
The base value for the submarine's health is rediculously low, considering it's made of metal and the cannons in use are fairly primitive, many being bronze based.

Combat Speed: 70 m/round
I've pushed the combat speed to 70 m/round to make this more comparable to other ships with a few upgrades.

Medicine, ammunition, and repair storage: 200
I don't think I've ever had trouble keeping supplies of these items, but once I obtained this ship I was at a high enough level that I began exploring the Deadfire in earnest. So increased supplies guarantees I can spend more time exploring, and less time resupplying.

Travel Speed: +30%
The base travel speed of the core ships, including the submarine, is 50. The TravelSpeed stat is actually a percentage increase on top of the base speed.

Looking at the upgrades available to other ships, I've modified the Fonferrus to have stats equivilant to the following:

Ymyran Steel Anchor: +5% travel speed
Arcane Lanterns: +10% travel speed
Blackwood Hull: +5% travel speed
Dragonwing Sails: +10% travel speed

Storage
Ammunition: 100
Medicine: 200
Repair: 100
While the submarine only has two guns, having only 50 ammunition is a rediculously small amount. Also, being a submarine, I would expect them to bring a lot more repair supplies than a normal ship, since they have to worry about hull breaches on all sides, not just underneath.

What this mod does NOT do:
This mod does not unlock the locked slots on the ship

Installation:
Extract the folder to Pillars of Eternity II\PillarsOfEternityII_Data\Override. You may need to create the Override folder first.

This mod can be applied at any time. I tested it with my current playthrough - However, your ship will remain at its current health and you'll have to repair to reach the new health limits.

Uninstallation:
Simply remove the folder from the Override folder.

Note that I have not tested removal to see what happens if the ship's health is above the vanilla level. So I would recommend making a backup save before removing this, in case it causes problems.

Customization:
If you wish to customize the values of this mod, simply open the file ships.gamedatabundle (In the Override > mod directory) in your favorite text editor. It is in C# syntax so if you use Notepad++ or an equivilant you can make things easier to read.

Here are the relevant line numbers and examples:

Maneuver Durations - Starting at line 49
"Action": "SailFull",
"IsAvailable": "true",
"Duration": 1

You'll see each action has a Duration, simply set the number to how many turns you wish it to take. I have not tested this with 0 turns and do not know how the game would react.

Supply Limits - Starting at line 185

"SupplyLimits": [{
"Type": "Ammunition",
"Count": 200
}, {
"Type": "Medicine",
"Count": 200
}, {
"Type": "Repair",
"Count": 200
}],

This is fairly self-explanatory, change the count for the corresponding supply limit to set your maximum.

Ship Stats - Starting at line 165

"BaseStats": [{
"ShipAttributeType": "CombatSpeed",
"StatValue": 80

For each type, simply set the StatValue variable. TravelSpeed is a percentage bonus on top of the base speed of 50. The others are normal values.