In 1873, John Philip Holland was a teacher and Irish immigrant to the United States that became temporarily bedridden after an injury shortly after arriving. Fascinated with submersible ideas, he used his bedridden time to design prototypes for submarines. At this time in history, submarines had significant issues with stability, reliability, and practicality and were generally not favored as realistic ideas by established navies.

While initially unable to find any Navy to fund his designs, the Fenian Society backed these seemingly science fiction schemes to build the first few protoptypes in the interest of using the submarines in the struggle for a Free Ireland. These initial prototypes were met with significant skepticism and had some initial trouble, but ultimately proved to work. Each iteration revealed new problems and Holland created new solutions.

The largest breakthrough that set the foundation for all modern submarine designs was Holland's recognition that the submarine must have a stable center of gravity and a different means of changing depth than a variable ballast. Holland's designs incorporated the idea that the ballast tanks must be fully empty or fully flooded to keep water from sloshing around; this keeps the center of gravity stable. With a stable center of gravity, the submarine could use diving planes that cause the vessel to dive or ascend based on their angle and forward movement of the vessel.

With the success of these prototypes, Britain took notice; various spy actions and legal matters arose in the US targeting the Fenian development of torpedo boats; concerned, a rogue group of Fenians stole the two prototypes, accidentally sinking one in the process. Holland felt he lost everything.

With no other prospects for further developing his submarines, Holland networked with some industrial investors and ship builders that would launch the Holland Torpedo Boat company, a subsidiary of Electric Boat. In the process, he gave up rights to all of his existing patents of submarine technology to Electric Boat.

The US Navy took interest and contracted Electric Boat to create the Plunger. Holland designed this, but was forced to meet the demands of the US Navy -- ideas he greatly disagreed with. The Navy wanted the vessel to be steam powered like all other current ships, but Holland knew this would simply cook the crew inside; they wanted a deck, which Holland refuted as egotistically motivated by officers -- "a deck to strut upon". Frustrated with these conventional ideas that he felt were ruining the ship, he convinced Electric Boat to begin work on a completely different vessel that he would design on his own -- the Holland VI.

This vessel was the culmination of all of his knowledge and ideas in submersibles and had the full support of Electric Boat. While the US Navy was skeptical about this boat designed by a school teacher, during sea trials, the admiralty was impressed; it completely outperformed any similiar vessel and fully showcased in plain sight a new effective weapon and technique in naval warfare. The Navy commissioned it as the USS Holland (later designating the class as SS-1) in 1900, making it the first real modern submarine in the US Navy, and placing the US as one of the first few nations to commission a real submarine.

The Holland VI designs were a large success for Electric Boat and this vessel type sold to multiple navies around the world, including the British. Over time, Holland had disagreements with Electric Boat board members over the company's lack of addressing safety concerns that led to several injuries and deaths aboard his ships. Holland resigned from Electric Boat in protest, and died not long after. Fortunately, he never lived long enough to see submarines become such a destructive force in naval warfare; he had hoped their covert nature would equalize disparities in naval forces and prove to be such a terrfying weapon that no one would use it, deterring naval combat all together -- the opposite became true, of course.

John Holland's achievements in submarine design have earned him the moniker of Father of All Submarines, as every submarine since the Holland VI has used his core principles and concepts in maneuvering and shape.

For a fairly whimsical but historical US Navy film on the subject, refer to: https://www.youtube.com/watch?v=kjxCyqzaHWU

Highly Recommended to have 3+ human players; few functions can be performed by AI.
(in order of significance)

Stands in the conning tower, using the periscopes (or sonar in mk2) to view the surroundings and issue commands to the crew. Recommend becoming versed in how to efficiently issue commands as well as familiarity with all functions of the ship. Example: Engines, Full, Ahead -- (who, what, more detail). (In mk3 variant, the captain/navigator can conduct full maneuvers with navigation console)

In the engine room, this operator controls the gears and clutches that change the thrust from the propeller and if the dynamo is charging the batteries. Recommend familiarty with engine controls, and how the gas engine powers the submarine.

Just aft of conning tower, helmsman adjusts the ballast tank with a flood valve and an air valve, as well as controls the diving engine (diving plane angle). Recommend familiarity with the helm maneuvering controls and principles.

In the forward compartment, this crewman loads, aims, and fires torpedos as well as triggers the dynamite gun on command. Recommend familiarity with gun systems and their limitations.

In the engine room, this crewman is on hand for monitoring power usage, alternating battery sources, and general upkeep of systems in the submarine.

Additional crew member on hand to assist others.

Gas Powered: The submarine is powered by a gasoline engine with limited gasoline. The gas tank is indicated in a guage above the engine. Gasoline is refilled automatically when the submarine is docked.
Engine: The engine turns the gears and prop shaft with approximately 45hp. Engine starts off. To turn on, use the Engine starter handle. Engine is on if light turns on. Note: Engine turns off if engine compartment is submerged in water.
Prop Shaft: The shaft can be used to either turn the propeller or spin the dynamo power generator, but not both at the same time. Use the clutch toggle at the dynamo to shift between powering the propeller or generating electricity.
Propeller gears: The speed of the propeller is controlled by the gears. To adjust the speed, use the engine reostat controls to either reduce RPM or increase RPM of the propeller shaft. A guage indicates the current speed. (Slow = 25%, Half = 50%, Full = 100%). Additionally, the engine operator can change the direction of the propeller shaft by operating the lever that toggles between Ahead (forward) to Astern (backwards).
Thus, if the command is "Engines, Full, Ahead" when previously the batteries were being charged and the submarine was at stop. The engine operator performs these steps:
1) Disengage the dynamo;
2) Set gear lever to "Ahead";
3) Adjust reostat to "Full" setting by turning the reostat with 3 clicks.
If the command is to charge the batteries; the operator can simply engage the dynamo clutch to generate electricity.

Battery Grid: 12 battery arrays of 60 cells are grouped into two groups (fore, cells 1-30, and after, cells 31-60). One group can output 24kW of power for 10 minutes. Only one battery group can be activated at once. Batteries cannot be charged while in use. Junction boxes that connect the battery arrays are in an accessible comaprtment directly beneath the conning tower.
Switchboard: The status of battery charges is indicated in the guages on the swithboard. Switches toggle between active battery groups. Junction boxes show the wiring from the battery groups to the using components.
Powered Components: Interior Lights (3kW), Exterior Lights (9kW), and the Aux. motor/air compressor (10kW) that provides ventilation and powers the ballast pumps and airflow.
Maintenance: Ensure all junction boxes are functional. Water can damage the boxes. Keep one battery group active to provide power to the submarine. The other battery group will be available for charging if the dynamo is on. You can turn both battery groups off to charge both groups if desired. Batteries do not charge unless dynamo is engaged (meaning the propellers are stopped). Captain should be aware of that this means the submarine must be stopped for a period of time for extended missions once power is running low.

Main Ballast Tank: The MBT is located in the belly of the ship. For a stable center of gravity, it is designed to be fully flooded or fully empty. The water level of the ballast is displayed on a gauge at the helm controls. It is filled with water by opening the kingston valve and emptied of water by blowing air into the ballast from the air tanks.
Diving Engine: Diving planes at the rear of the vesssel can be angled up or down to direct the vessel up or down when under thrust. The rate of the ascent/descent provided by the diving planes is proportional to the speed of the propellers. This is controlled by the diving engine lever.
For Maneuvering conditions: The helmsman should flood the ballast tanks by toggling the flood valve open and then closed. This fills the tanks and makes the vessel have a small neutral buoyancy (slowly descends). With ahead or astern movement, the diving planes can be used to cause the vessel to further ascend or descend as ordered. Faster propeller speeds means faster ascent/descent. In event of tight vertical corridors, the crew can safely slowly descend without movement or attempt to perform short bursts of alternating forward and backward movement.
Neutral Buoyancy: The vessel has a small net negative buoyancy with full ballast tanks. To attempt to hover at a certain depth, the operator can attempt to ensure the flood valve is closed, then quickly toggle the air valve on and off until neutral buoyancy is achieved.
Surfacing/Ascent: To ascent or surface, the operator needs only ensure the flood valve is closed and open the air valve to fully empty the ballast tanks.

Torpedoes: The submarine has a forward mounted fixed torpedo tube that launches torpedoes. The standard loadout includes 3 torpedoes. The stock torpedoes have high explosive payloads. The gunner can use a sight to aim the torpedo by using the periscope near the tube. The tube can be reloaded as quick as the gunner or assistant can reload the tube.
Dynamite Gun: There is also a dynamite gun/projectile tube pointed to the upper bow at approximately a 35 degree angle. This fires explosive rounds but requires 10s to reload and has no aim sight for the gunner. The Captain should observe the target area and provide firing commands to the gunner for usage of the dynamite gun. The firing trigger for the dynamite gun is through the periscope near the gun loading area.

The Captain can gain situational awareness of the surrounding terrain by using the 3 periscopes in the conning tower. These periscopes offer views to the upper right, upper left, and lower areas in the vicinity of the submarine. The visibiltiy is limited and requires the Captain to untuitively understand the terrain layout and carefully gauage the maneuvering commands given. (mk2: This variant gives the Captain an anachronistic sonar station to provide easier navigation)

Tool Storage: A chest by the helm and aux. motor provides storage for tools and maintenance equipment.
Diving Suits: A large chest forward of the conning tower provides storage for 6 diving suits.
Misc Storage: A small crate forward of the conning tower provides storage for the crew as needed.
Medical Storage: A small crate forward of the conning tower has basic medical supplies.

A lock for the top hatch is above the helm station as well as a toggle for the docking clamp.

A manual hand pump is used for bilge water. Rapidly click the hand pump handle to slowly pump out the water. (mk3 has automatic pump).