St John said it was notified around 3pm and responded with one helicopter, one ambulance and three rapid response vehicles.
A Coastguard NZ spokesperson said it had volunteers on board two rescue vessels from Coastguard Sumner – Hamilton Jet Rescue and Blue Arrow Rescue – searching for the missing swimmer. Its jetski, Bruce Dawn Rescue, is also actively involved in the search.
“All vessels are currently conducting a search offshore between Southshore Spit and Sumner Beach,” the spokesperson told the Herald.
“There are six volunteers aboard Blue Arrow Rescue, three aboard Hamilton Jet Rescue, and one on Bruce Dawn Rescue.
“Search conditions are challenging, with overcast weather, a 1-1.2m swell, and poor water visibility. The outgoing tide and wind-driven swell have further complicated efforts.”
Sign up to The Daily H, a free newsletter curated by our editors and delivered straight to your inbox every weekday.