Treacherous swimming conditions on east coast beaches kept lifeguards busy yesterday watching over crowds unable to resist 2m swells from Cyclone Waka.

Whangamata head guard Ben Jansen said conditions were very dangerous.

"We've got a howling offshore, too, which is great for surfing but can dump a swimmer."

Up to 4000 people headed to Whangamata yesterday but most stayed between the flags.

"It's so dangerous, and most of them have noticed that," Mr Jansen said.

Lifeguards had made "quite a few" rescues over the past two days, including one woman who had an epileptic fit in waist-deep water between the flags.

Hamilton man Dave Burbage emerged from the surf at Whangamata yesterday to describe the spectacular conditions.

Mr Burbage, who has surfed at the beach since 1965, said:"One of the waves I got out there, as soon as I was on it I thought: 'Hell, I'm gone for'. Then it was into the washing machine ... It was magic."

Mt Maunganui lifeguard Adam McGarvey also said 2m swells were rolling in.

Crowds had dropped off slightly yesterday, but several boogie boarders had to be rescued after being caught in rips.

MetService marine forecaster Jan Hoeksma said most of Waka's swell was now directed at the South Island, but he expected swells to stay about 2m on the North Island's east coast for the next two days.