HSwMS Näcken was the lead ship of her class of submarine for the Swedish Navy.

From 2001 to 2005, the submarine was leased to the Royal Danish Navy and operated as HDMS Kronborg (S325).

This new diesel, the Stirling V4-275R, provides air-independent propulsion which allows the submarine to operate continuously underwater.

This comprised improved weapon control systems, automated torpedo tube loading and new sonar.

[1] Näcken was transferred to Denmark in 2001 as part of a deal for the design and construction of the Viking-class project.