This is a form of Watercraft that may operate underwater but must periodically surface for air.
- The crew require air to breathe and the supply aboard is not supplied by a renewable life-support system
- The power generation system is an Internal Combustion Engine or other air-breathing Powerplant, and the power storage system must be recharged.
Other than this limitation, these vessels have the abilities and limitations of Submarines
Submersibles may be constructed at lower technology levels for military purposes, but at higher technology levels, they become primarily the playthings of the civil world. The exception is on Waterworlds where Submersibles are often indispensable parts of the world's transport network.