Dangerous snorkelling tours are taking place in Rarotonga's Avaavaroa passage, the Cook Islands Water Safety Council says.
The council's president, Brent Fisher, said the tours to see turtles had only been happening for about a year, and some participants had felt in fear of their lives.
"It's a big passage that goes right through the reef. Most of the time you've got quite a major flow of water going in or out... and you get a current sucking down as well. You can get sucked in underneath the cliffs that are on the side of the passage," he said.
"We've got interviews with people that have been scared for their life."
People had previously drowned in the passage and most tour operators were not trained in the risks, Mr Fisher said.
"The safest time to do any sort of tour like that, not that it's actually safe, but the safest time is on a low tide. So you've only got maybe an hour that you can operate it sort of semi-safely. What's happening is some tour operators are taking out four tours, one after the other, so they're way outside the safer time that they should be running it."
The council wants all the tour operators to undergo a mandatory safety course which it's in the process of designing, he said.
"We've got a guy coming over from Australia to help and we're hoping to have that up and running within about two months. Then we'll be looking for the government to legislate which the police are 100 percent in favour of happening. Of course some of the operators aren't but we've got to do something.
"We're basically just waiting for someone to drown."
"The course would take "four or five days" to complete and the cost of participation would hopefully be subsidised by the government," Mr Fisher said.
"If so, the cost per individual could be about $NZ50."