The group - a man wearing pirate accessories and three women - was boating down the river near Albert Town in three inflatable dinghies, when a resident noticed them just after 7.30pm and alerted Queenstown Lakes harbourmaster Marty Black.
''He was concerned for their safety because not one of them was wearing a life jacket, so he called me,'' Mr Black said.
''I contacted a staff member who lives nearby, and he picked them up just above the Albert Town bridge.''
When the four people were summoned off the river, they claimed to have no idea they should have been wearing life jackets.
Three were New Zealanders and one woman was from Germany. They were in their 20s and ''should know better'', Mr Black said.
Their breach of the Queenstown Lakes District Council navigation safety bylaw cost them each a $300 fine.
Last week, two tourists kayaking separately on Lake Wakatipu without life jackets were also issued fines.
Mr Black hoped the latest incident would help enforce the message that everyone had to wear a life jacket at all times if they were on the water in a boat under 6m in length.
About 30 offence notices had been issued to people last summer for not wearing life jackets, but the issue seemed to be cropping up earlier than usual this year, Mr Black said.
