A close friend who tried to save Judith "Judy" Lorraine Palmer, 62, from a lagoon yesterday also drowned.
Mrs Palmer was the wife of Chief Inspector John Palmer.
Close family friend Robert "Bob" Groves, 64, was also there with his own wife for the wedding, police said.
The couple were neighbours in Auckland's Birkenhead.
Mrs Palmer had been swimming in a lagoon near where she was staying.
The bodies of Mrs Palmer and Mr Groves were recovered about half an hour after the tragedy, police said.
The group was in Vaimaanga, Rarotonga for the Palmers' daughter's wedding, which was scheduled for today but has since been postponed.
Auckland City District Commander Superintendent Mike Clement said: "We are all reeling from the news and can only imagine the magnitude of the devastation John, his family and the Groves family are feeling.
"I know personally that the trip to Rarotonga for Vanessa's wedding was to be the highlight of the year for John and Judy and that much planning and anticipation surrounded it.
"I and Commissioner Peter Marshall have spoken with John on several occasions in the past 24 hours and have offered our absolute support and assistance to help him, his daughter and their friends through this very distressing time.
"Commissioner Marshall has also spoken to the Commissioner of the Cook Islands Police and thanked him for the support he is giving to the Chief Inspector and his family.''
John and Judy Palmer had been married for 42 years.
Chief Inspector Palmer has served with New Zealand Police for nearly 47 years, much of which has been in Auckland City District.
