A swarm of jellyfish forced the closure of Oreti Beach in Southland on Sunday.
Hundreds of stinging blue bottles, also known as Portuguese Man o' Wars, were spotted in the surf, forcing the surf club to close the beach to all but four wheel drive vehicles.
Surf lifeguard patrol captain Robert Cole told Summer Report he made the decision to clear the water because jellyfish can cause a sting strong enough to hospitalise someone.
He said there were hundreds in front of the swimming area by 2.30pm.
He expects winds overnight will have driven most of the jellyfish away.