The man, with no lifejacket or flotation aid, was reported to police as needing help about 12.20pm on Saturday.
He had been taken out to sea at the Waitaki River Mouth, and spent about 45 minutes in freezing water before being rescued, police said.
"While it is fortunate that emergency services were contacted and provided a swift and successful response in this instance, it’s a reminder that water safety is key.
"Police urge anyone going near waters, no matter the skill level, to take the basic precautions to keep themselves safe in case something goes wrong.
"Tell someone where you are going and when you will come back - this can be crucial information for us to locate you."
Police are reminding people to always were a lifejacket when boating or fishing, and have a waterproof bag to put their phone in the jacket.
Swimmers and surfers should stick to their limits and not go in the water if in doubt about the conditions.
"Be aware of your surroundings and the dangers they may have - check the local marine weather forecast before you go and expect both weather and water state changes.
"Our Southern rivers can be dangerous, and with the incoming winter weather, the water temperature is much lower, meaning it will be less likely you’ll survive."
