There are two public access sub bays on the NSS Manta, one called Submarine Bay (Port), which is on the end of the hallway that starts west of Arrivals and goes past Cargo, and the other called Submarine Bay (Starboard), which is on the end of the hallway that runs east of the Rising Tide bar and goes past Medbay and Research. Both are almost exact mirror images of each other.
Both bays start with four (4) standard, white mini-subs. To outfit and maintain these subs, each bay has a ship component fabricator, a mechanical toolbox on a table beside it, and plenty of welding supplies for repairs, specifically a large tank of welding fuel, a crate with handheld welding fuel tanks, and a welding supplies locker with welders and welding masks.
Each bay also has a cyborg docking station for cyborgs and an emergency oxygen closet that may or may not contain a full internals set, depending on your luck. In addition, each bay inexplicably has slightly different tools lying on the floor; the Port one has a wrench and a crowbar, while the Starboard one has a wrench, screwdriver, and multitool.
Neither sub bay has a vent. Vents don't go on subs anyway.
The APCs for both rooms are on each room's northern wall, near the ship component fabricator.