Lt-cmdr Marshall planned to leave Dunedin's Royal New Zealand Navy (RNZN) base HMNZS Toroa and depart New Zealand tomorrow.
His 12-month deployment left a vacancy, applicants for which would be interviewed in coming weeks.
An RNZN spokeswoman said the position would be amended from a Regional Naval Officer (RNO) to an Honorary Naval Officer (HNO).
''The selection process for filling this position is already under way. I can reassure you there won't be a gap for 12 months whilst Ian Marshall deploys to South Korea,'' she said.
The navy recognised the value of having representatives throughout New Zealand, including Dunedin, and the position change was in line with a restructure of regional support nationwide, the spokeswoman said.
''After the Dunedin position is included, the navy will have a total of 15 HNOs spread across all regions.''
A position of Commander Naval Regions was established at the Devonport naval base, and the incumbent Commander Frank Rands would ensure a greater level of support to regional representatives through constantliaison, she said.
The RNZN was also working to integrate all HNOs in the Royal New Zealand Volunteer Reserve.
''We certainly appreciate the great work that Ian has done in the Otago region. He is a proactive individual, who has represented the navy with honour, and we wish him the very best in his new adventure,'' the spokeswoman said.
In Seoul, Lt-cmdr Marshall will help monitor the armistice agreement between North and South Korea, in the 60th anniversary year of its signing.
He was one of three New Zealand Defence Force personnel selected to replace those finishing a six-month deployment in the capital.
Lt-cmdr Marshall volunteered for the posting, which he looked forward to.
On his return to New Zealand he would be able to negotiate a position in the RNZN based on his preferences.
