A man and woman are dead and another person is in a serious condition after a water emergency near Raglan this evening.

Police were called to Ruapuke Beach, between Raglan and Kawhia on Waikato's west coast, at 5.30pm.

Police said a woman in her 40s was dead and another person was pulled from the water.

The survivor was airlifted to Waikato Hospital in a serious condition by the Westpac Rescue Helicopter.

A third person, a 33-year-old man, was initially reported missing.

His body was found by a Coastguard vessel about 6.40pm.

Coastguard, surf life savers, firefighters, police, ambulance and search and rescue volunteers were all called to the incident.

The circumstances of the incident were initially uncertain due to language difficulties.

Police will be investigating the deaths on behalf of the coroner.

Earlier today, a male teenage swimmer was swept out to sea after being caught in a rip at a Whanganui beach.

Emergency services were called to Castlecliff Beach about 3.55pm.

Police search and rescuers were searching for the the 17-year-old Whanganui local with the help of Coastguard, a local helicopter operator and the Taranaki Rescue Helicopter.

Across on the east coast, a 3-year-old boy died in a lagoon at Ocean Beach near Hastings.

The child was at the beach with extended family and friends and died at the scene after being found by family in the estuary.

A police spokesman said the incident was "very tragic".

Surf Life Saving New Zealand's programmes and service manager for the central region Jacob Davies said two guards were called to the scene.

He said surf life savers were on patrol as part of the regional guard service and they were contacted by the public from the patrol area to come and assist.

"Our lifeguards were involved today they were contacted around about 2pm to attend an incident that a member of the public alerted them to, that was in lagoon about 400m away from the flagged area," he said.

"When they arrived they undertook first aid on the scene.

"There were two life guards and they did CPR for 40 to 45 minutes with the assistance of other members of the public until they were taken over by the fire crew and the helicopter."

Members of the Havelock North Volunteer Fire Brigade were called to the beach. They could not comment on what had happened.

The child's body was flown to Hawke's Bay Hospital by the local rescue helicopter service.

Hawke's Bay Lowe Corporation Rescue Helicopter pilot Russell Mardon confirmed they attended an incident at Ocean Beach but was unable to provide any further details.

He said the beach, just south of Cape Kidnappers, was a popular swimming spot.

Mr Davies said while he was unaware how the incident took place or arose, people must make sure that children were watched at all times when they were in the water.

"I have no background details of how this happened but it is just making sure that supervising your children," he said.

"And if you are of that age ... you always swim with someone else."

Police were investigating and the death would be referred to the coroner.