So I've been toying with stating out the Nautilus (crazy I know) and Nemo's Underwater Electric Pellet rifle.
Crew is problematic. Verne never states exactly how many crewmen are aboard. At least 20 according to one passage and probably no more than 25 considering all the schematics I've seen. That leaves Captain Nemo and the 3 passengers from the novel. Despite that, I'd peg the maximum number of passengers to be double that.
Since the rules for ship to ship combat in 3.5 aren't open content; I'm substituting the Pathfinder rules on ship combat. If you need to refer to them they are here: http://www.d20pfsrd.com/gamemasterin...es/ship-combat but I'm also using updated stats from Skull & Shackles Player's Guide (http://www.d20pfsrd.com/gamemasterin...combat/vessels)
Here are a variety of designs for the Nautilus, though many will be most familiar with the Harper Goff image from the Disney movie. http://www.vernianera.com/Nautilus/Catalog
And this is the Goff image
The Nautilus submarine is a both a work of art and a feat of engineering made by the brilliant and xenophobic Captain Nemo and his crew of submariners. Nemo's relentless urge to avenge the deaths of his wife and two children drive him to the brink of madness. He blames not just the politics of his own country but for all countries and uses the Nautilus as a weapon of vengeance. In stark contrast, he cares deeply for his crew and has a strong affinity for the preservation of the natural world.
The Nautilus is a steel clad submarine, 230 ft. in length and 26 feet wide. Her double hull is a unique feature and she is able to move at incredible speed due to her electrical propulsion system. Her attacks on ships imitate that of a monstrous narwhale as she rams them and punctures them with her ramming prow. When she rams a ship, she not only takes no damage from the attack, but also appears to pass "through the mass of the vessel like a needle through sailcloth" as described in the book.
She has desalination equipment aboard but needs to refresh her air supply, which blows out like a whale. Her maximum dive time is 5 days. Her windows are made of glassteel, making them impervious to water pressure at great depths. Despite her maximum speed, she generally cruises at much lower speeds.
The elaborate and luxurious interior of the grand salon, which reaches the height of both decks, includes a massive organ, an invaluable art collection along with a collection of pearls, coral, and other marine products. It also houses a fountain made from a giant shell. Nemo's library holds an impressive 12,000 volumes. Both rooms are exquisitely furnished in sharp contrast to the stark quarters of the crew.
Size/Type: Colossal submarine
Propulsion: Electrical machinery of unique design
Driving Check: Knowledge (architecture and engineering) DC 15
Forward Facing: The submarine's forward
Driving Device: Steering wheel
Driving Space: Enclosed 5 ft. by 5 ft. wheelhouse that retracts when the submarine prepares for a ramming attack
Weapon: Ramming prow. Because her ram is under the waterline, ships rammed by her gain the broken condition when they lose 1/4 their hit points instead of the normal 1/2. They still do not sink until reduced to 0 or fewer hit points.
Maximum Speed: 50 knots (440 feet).
Armor Class: 10
Hit points: 4,600 (2,300)
Cost: Not for sale
Space3:230 ft. long 26 ft. wide
1 No more than 20 ever appear on deck at once. Since the crew's quarters are only 16 feet long, this is the limiting factor.
2Because the Nautilus rams ships below the waterline, any ship that is successfully rammed gains the broken condition when it loses ¼ of its hit points rather than the normal ½.
3 In order to play out ship-to-ship combat on a Flip-Mat or battle mat, a single square on the map corresponds to 30 feet of distance, rather than 5 feet. Most ships are long and thin; rather than taking up a space of an equal number of squares per side like creatures do, a ship's width is always considered to be one square. The nautilus takes up 7 squares in length and 1 square in width.
The following are taken and adapted from standard Pathfinder rules for sinking other ships.
Broken Condition: Ships—and sometimes their means of propulsion—are objects, and like any other object, when they take damage in excess of half their hit points, they gain the broken condition. When a ship gains the broken condition, it takes a –2 penalty to AC, on sailing checks, and saving throws. If a ship or its means of propulsion becomes broken, the ship's maximum speed is halved and the ship can no longer gain the upper hand until repaired. If the ship is in motion and traveling faster than its new maximum speed, it automatically decelerates to its new maximum speed.
Sinking Condition: A ship that is reduced to 0 or fewer hit points gains the sinking condition. A sinking ship cannot move or attack, and it sinks completely 10 rounds after it gains the sinking condition. Each additional hit on a sinking ship that deals more than 25 points of damage reduces the remaining time for it to sink by 1 round. A ship that sinks completely drops to the bottom of the body of water and is considered destroyed. A destroyed ship cannot be repaired—it is so significantly damaged it