After 10 years of operational experience with the Delphin coastal defense submarine, Brick Isle embarked on the rapid construction of the Neptune. She was constructed in less than 2 months in late 2017. Significant materials were obtained from multiple sources from across the U.S. due to the specific requirements for the hull.
This submarine is a full-fledged attack submarine of over 200 feet in length. She has a complement of 36, with four torpedo tubes forward and two rear facing.
The diving planes are mounted on the sail and are functional, being rotated by the periscope mast.
Just prior to launch, a solution was found to build the X shaped tail fin of the original design. This necessitated dismantlement of a fully complete vertical tail arrangement. The X configuration is expected to improve maneuverability and shallow water operation.
The Neptune is too large to operate from the dock in the fjord used for Delphin and her home port is the more modern naval dock near the city.