The torpedo-shaped UUV, designated the AUV62, can be launched from surface vessels, submarines or from land and comes with modules for anti-submarine or mine-hunting operations.
The system was developed by FMV in partnership with the Swedish Defense Research agency and Saab.
"Flying drones playing an increasingly important role in conflicts around the world," said Carl-Johan Andersson, a development engineer at FMV. "But unmanned craft could be at least as important under the surface."
For mine-hunting mode, the AUV62 is equipped with a synthetic aperture sonar that tracks the movement of a vessel on all planes and includes the data with an image of sonar echo to determine the precise position of a mine.
In hunting submarines, the system locates a target using both sonar echo and noise.
FMV said the UUV62 is being tested by the Swedish military in submarine detection exercises.
"Today AUV62 can run 20 hours at a speed of 4 knots," the agency said. "One possible vision for the future is to replace batteries with fuel cells and get significantly longer endurance. Then the craft could leave harbor in underwater mode along with the mother ship."
FMV said Saab has completed a first contract for the system and more contracts are expected.
The UUV62 is about 21 feet long and has a maximum endurance of 20 hours.