When they arrived at the Naval Yard, the vessels' commanders were ordered to warn their crews to observe strict silence about their movements and were told that the three ships had been picked for a "special purpose".

[1] The Vigra and her sister vessels superseded the famous fleet of civilian fishing boats that had formerly run naval operations between Shetland and Norway.

During the final two years of World War II the three ships performed a total of 114 missions to occupied Norway, and apart from one incident when a Canadian aircraft fired on Hessa, the voyages were uneventful and there were no casualties.

All three submarine chasers were mothballed at Marvika and formally decommissioned in 1959.The Vigra was first sold to Sea Scouts for 1 NOK and finally sank near Malmö where she was used as a sand barge.

[5] The name HNoMS Vigra is today held by a smaller patrol vessel used by the Norwegian Naval Academy for Officer cadet training (P359)