The Queenstown Lakes District Council wants wearing a lifejacket to be compulsory by the end of summer for anyone on a boat.
Four people have died on waterways there in the past month - the worst toll in the district for 25 years.
On Monday, two men who were not wearing life jackets died after a collision between a jet boat and a jet ski on the Kawarau River.
Last month, a man was killed in a jetboat crash on the Matukituki River, and another man drowned in Lake Hawea.
District chief executive Duncan Field says the council is putting a bylaw in place to make wearing a lifejacket on a boat compulsory. He says this will enable the council to penalise people who ignore the rule.
Harbourmaster Marty Black says the bylaw should come into force in a month and will be strictly enforced.