Mount Maunganui Main Beach lifeguards had one of their busiest days on record yesterday when a vicious rip whipped up by the aftermath of Cyclone Waka sucked out 38 swimmers.

No one was spared, not even surfers or boogie boarders wearing fins. Lifeguards reached everyone quickly enough to avoid any close brushes with drowning, although one girl was so distressed she needed oxygen to settle her breathing.

Regional lifeguard supervisor Brett Girven said the nine lifeguards started pulling people out in bunches of two or three from 2pm, after which it was "pretty much constant" until 7pm.

Nearly half the rescues were boggie boarders: "It was an unbelievably strong rip. Even experienced surfers could not paddle against it."

Surf of about one and a-half metres made the rips start to work on the low tide, with a big rip developing toward the Moturiki (Leisure) Island end of the flags.

Mr Girven said it was so strong that swimmers were unable to keep their feet beyond waist deep.

At one point, one of the two inflatable rescue boats broke down and in just one minute it drifted 300 metres to be out by the blowhole.

He rated the afternoon's work as up among the top five busiest days ever: "The lifeguards did a great job keeping everyone safe."

Flags were moved back toward the surf club, but the rip was not static and a lot of bathers tended not to follow the flags to the full extent that they should have. Patrols finished at 7pm when everyone left on the beach were told they should not swim anymore.

Mr Girven said Omanu and Papamoa beaches were quite quiet by comparison. He was not ruling out more rips today. Mid-afternoon would be the key time -- half way to low tide.