Sul

The Sul is a custom variant of the Atlantica sub and can be purchased from the ship trader at the Spirios Shipyards for 35000 gold after the player purchases the level 3 upgrade to their subs.

The Sul is the largest sub the player can acquire and easily dwarfs the Manta, the second largest sub in the game. It boasts a menacing arsenal of 12 bolt cannons, spread between two triple gun turrets (dorsal and ventral) and three dual gun turrets (dorsal, ventral and aft), though it can only bring all of them to bear when presenting a broadside. With this many bolt cannons, it can not only rip other subs to shreds with virtual impunity, but it can also easily shoot down incoming torpedoes as there are always guaranteed to be multiple guns pointing at an incoming torpedo.

At 85 hull points, it can comfortably trade hits with any other sub in the game, including the Naglfar which doesn't possess enough firepower to take the Sul down before it disables all of its guns.

On top of being extremely tanky, it also possesses a crew capacity of 20, allowing you to maintain a large repair crew to quickly repair any damage sustained during combat with or without repair kits, all while fully crewing every station.

Its downsides come in the form of its underwhelming cargo capacity, horrible maneuverability and sheer size.

The cargo capacity of 20 makes Forgotten Fjords Wandering Merchant hoarding trips somewhat less viable, though by the time you acquire this ship it's highly unlikely that you will need to buy anything else except for food and oxygen tanks so min-maxing your profits becomes pointless.

The poor maneuverability and its sheer size (as awesome as it is) make it extremely awkward when trying to dock with anything as the ship tends to ram itself into whatever its trying to dock with and break the docking cables several times before successfully docking. Additionally, the ship has two massive aft engines mounted in downwards-sloping wings (think USS Enterprise but upside down), which have a tendency to latch onto things as you pass near them, making docking and navigation around narrow spaces even more awkward. However, you'll be spending most of your time in open waters, where your poor maneuverability and size don't factor into your ability to obliterate anything unfortunate enough to be marked as hostile by your sonar officer.

Notes:

 * The game claims the Sul to have 28 bolt cannons in the purchase/swap menus, however as mentioned before it only appears to have 12 bolt cannons in its turrets.
 * It's interesting to note that the ship has a large number of sponsons on its broadsides aswell as a large number of small gun turrets on the top of its bridge, however none of them hold any bolt cannons and none of them seem to move. It's possible that the developers intended for the Sul to have bolt cannons in these locations because there are other subs in the game with working small gun turrets (Manta) and sponsons (Beluga) that look similar to the ones on the Sul, however they might have scrapped the idea to avoid making the Sul even more absurdly overpowered than it already is.