Four people have escaped drowning in two separate incidents on each of Auckland's harbours, say police.

In the first incident, police say two people were assisted from the water when their inflatable pool toy overturned, out from the Bayswater Marina in the Waitemata Harbour.

Only one of the two was wearing a personal floatation device, say police. Both were returned to shore at the marina.

Police say in the second incident, two female teenagers were blown about 1.5km off-shore from the Awhitu Regional Park on the Manukau Harbour.

"They were riding on a white inflatable pool toy swan. The two were returned to shore by a boat that had gone to rescue them and the personal water craft that had originally been sent to assist the girls."

Police are concerned for the safety of people using these toys.

"These are not boats and should not be used outside of a small sheltered swimming pool," says Sergeant John Saunders of the Police Maritime Unit in Auckland.