Police are investigating what they say was a vicious and cowardly attack at a school swimming pool north of Auckland.
They say a woman in her 20s was indecently assaulted at Mahurangi College just after 7pm on Thursday.
Detective Senior Sergeant Brett Batty says the man fled the scene, possibly after hearing someone else in the school grounds.
He says officers, a police helicopter and sniffer dogs searched the area after the attack, but were unsuccessful
Police have described the man as a dark-skinned, in his 20s, and say it appears english was not his first language.
Members of the public who saw or heard are urged to contact police.