merindian submarines

The Merindian Empire heavily utilized submarines to help achieve it's many goals.
Merindia has the largest submarines in the world, as well as the largest number of them. Merindian military submarines are very large and powerful, with advanced sonar and navigation technology, and armed with powerful torpedos. These submarines can sneak underneath enemy ships and launch surprise attacks. These submarines are the largest in the world, reaching up to 600 feet and can comfortably allow crew member to live on it for up to half a year. Military submarines are all large, cigar and lacking windows, with the crew detecting what's happening outside of the submarine with sonar and radars, and parascopes if they're close enough to the surface. All military submarines can cross over into the outlands and back. Military submarines often dock at underwater bases. These bases vary in size, but all of them can support multiple docked submarines and have crew working on it at all times. The locations of these underwater bases are kept secret, and they are very useful to the Merindian Empire.
Civilian-use submarines are a lot different, they are often shaped differently and feature many windows, as well as lights for visibility. These submarines are sometimes used as an alternative to airship travel, both airships and submarines have similar accommodations for passengers, making this like underwater moving hotels, but submarines have more space in them as they don't need space for lifting gas, but they can't go above land like airships can. Submarine travel is highly developed, submarine liners run from Merindia to the outlands and back. There are many privately owned submarines, and some rich people have even taken to fully living in them.
Exploration submarines are widely used, but most of them are used by the Explorer's Guild. Exploration submarines are the smaller than military and travel submarines, and are used to explore and research the ocean. Exploration submarines often feature large windows, arms to grab objects and put them in special holding chambers. Some exploration submarines are very large, able to accommodate a full crew for several months underwater to perform research, although there are only a few of them, all of which are owned by the Explorer's Guild.