Surf Life Saving New Zealand expects to rescue about 1200 beachgoers from life-threatening situations this summer.
Chief executive Paul Dalton said many of last summer's rescues took place outside patrol hours and flagged areas.
He said five of the eight people who drowned on beaches last year were parents or relatives rushing into the water to help save their children.
Mr Dalton is calling on people to take precautions such as swimming between the flags, keeping an eye on children and not swimming alone.
He said 4000 lifeguards will be on duty at 80 beaches this summer.