Two mass rescues, each of more than a dozen people caught in rips, took place at northern beaches on their first hot Saturday of the season.
Surf Life Saving's Northern Region, which covers Auckland, Northland and Raglan, said 46 people were rescued across its beaches.
One of the mass rescues was at Auckland's Muriwai, and involved 13 people being brought back to shore.
They got into strife when a couple of rips suddenly opened up while several hundred swimmers were in the water.
Surf Life Saving Northern said the second mass rescue, at Raglan in Waikato, saved 14 people.
Two lifeguards used an inflatable boat to pull people from the rip and deposit them safely on shore, and returned several times to retrieve more.
The day's multiple rescues were "a timely reminder of the dangers of the surf environment and how quickly conditions can change", a spokesperson for Surf Life Saving Northern said in a statement.
"The message from all patrol captains today was the importance of swimming in between the flags, especially in treacherous west coast conditions."
Meanwhile, Hamilton police are urging the public to use common sense if they are heading into the water this weekend, after being called to multiple rescues in the Waikato River in recent days.
Hamilton City Area Commander Inspector Andrea McBeth said while the river may be a tempting spot for a quick swim, it has fast flowing and changeable currents, with whirlpools in some parts.
McBeth said to ensure safety, it's important to be prepared - know the water and weather conditions before you get in, and always swim with others.