Clockwork Nautilus

The Clockwork Nautilus is a Gnomish invention to covertly transport goods over long distances. The machine is designed to look similar to the nautilus creature but much larger, the shell of it looks natural so it may blend in with other ocean creatures. The hull is magically enhanced to withstand high water pressures so that it can travel at depths that are less detectable.
The cargo bay of the Nautilus is engineered for maximum storage, and includes hidden compartments within the spiraling shell. The entry to the cargo bay is locked with reinforced doors with clockwork mechanisms to prevent access. The sub is internally lit by Bioluminescent pearls which have been harvested from rare deep-sea oysters, they give off a soft eerie glow lighting the interior just enough to navigate through the hull. To detect potential threats and obstacles, the sub is equipped with a magical sonar echo device that renders acoustic images of the surrounding environment on a magical tablet. The navigation system is comprised of a magical compass, depth gauge, and various nautical maps. There is also another unique feature of the sub where if it stops moving it can activate camoflauge like an octopus. The Nautilus is capable of staying submerged indefinitely due to having waste processing systems, and magical air filtration systems that can use water to refresh the air.
The Nautilus is incredibly expensive due to all the materials and craftsmanship required to build it. Only the richest nobles can afford to have goods shipped using the Nautilus and because of this there is often nefarious goods shipped through them. There are some Nautilus owners that operate solo out of various freeports, they operate at a very high price and only the highest ranks of black market folk even know who to contact to contract one of these couriers.