"There were 23 preventable fatal drownings in rivers in 2016, representing nearly a third of all preventable drownings. There were 13 in 2017."
He said rivers were often unpredictable, containing hidden dangers and changing after heaving rainfall.
"Anyone who can't swim should stay out of the moving water. Rivers are generally unpatrolled — you should never swim alone and, before you enter the water, you should get local knowledge about the conditions and always establish an exit point."
Even strong swimmers should avoid swift currents.
"Only swim in river pools where the water is calm," he said. "If the river level appears high, the water is discoloured and moving swiftly, people should not enter them."
The Rangitikei River was notably discoloured and higher than usual after recent rainfall. Horizons Regional Council catchment data senior co-ordinator Brent Watson said recent thunderstorms would have affected the clarity of the water, however there was only a small increase in its flow.
"The Onepuhi site, upstream of the Bulls Bridge, saw the river flow increase to 53m3/s over night (around median flow), river height rising approximately 0.15 meter over Sunday. This is still quite low; 'flood flows' for this site are above 500m3/s."
Recent testing at the site had also revealed unsafe levels of E.coli. HRC science and innovation manager Abby Matthews said these levels meant the water was unsuitable for swimming.
"The site has signage in place to show where people can go for the latest data. Our swim spot water health monitoring forms part of Council's larger safety messaging around swimming in our region's waterways."
She said they also wanted to remind people to check for potential hazards, cyanobacteria and avoid swimming for three days after rain. "The latter is of particular note as the current conditions (hot weather interspersed with rain events) can result in high flows, even on hot sunny days which entice people to swim in our rivers. When it comes to safety at our rivers and beaches, it always pay to err on the side of caution — if in doubt, stay out."