The Cook Islands Tourism chief executive says Avaavaroa Passage, which is a popular turtle swimming spot, is notorious for drownings.
Tony Thorp, a 50-year-old New Zealand man, died in the passage on 18 December.
Thorp was in Rarotonga for the wedding of his sister, Sarah Thorp-Adams.
Thorp-Adams said in a written statement her brother drowned in a dangerous rip.
"Bystanders and locals tried to save him and nearly drowned themselves, but he couldn't hang on any longer," she said.
"He did try; he did fight.
"Tony had a huge love for water and wanted to see some turtles before he was supposed to fly back to NZ.
"We are in shock and shattered beyond repair."
A police spokesperson confirmed Thorp had drowned based on the Coroner's report.
Sarah Thorp-Adams said Tony's "beautiful, loving and kind partner" Zoe had gone to the scene.
"Then Mum, Dad, Jase and I drove there, spent time with him on the beach before he was taken away."
"Rest in love my only sibling, my brother, a son, a father, loved partner by Zoe, a nephew, a cousin and friend."
Thorp-Adams said her brother was a great swimmer and was a trained diver.
But he had a sore ankle so did not wear fins when he went into the passage.
She said he was out there for 10 minutes in shallow water before he got into trouble.
Tourism boss Karla Eggelton said over the last year, lots of work has been done to educate visitors about the dangers of the passage.
She said signs also tell people not to swim.
"Avaavaroa passage is an opening from the lagoon into the Pacific Ocean and with that, there are some strong undercurrents that can take you out of the lagoon into the ocean, especially during high tides," she said.
"That has been a real critical issue with passages not just in Avaavaroa in Rarotonga but across the Pacific."
Eggelton said swimming with the turtles had become one of the top three tourism attractions for the Cook Islands for visitors and regulations were needed.
She said the issue was being looked at by Cook Islands Tourism to ensure the passage's biodiversity remained and visitors stayed safe.
Eggelton confirmed new regulations were expected to come into force in the next 12 to 18 months.