Pair drown in Queensland dam

The brother of a woman who drowned along with a teenage boy at an Australia Day party in Far North Queensland has paid tribute to her.

Kirsty Cini and the boy, 15, died at a Julatten Dam on Friday afternoon, with acting police Inspector Rob Campbell saying the 24-year-old went limp as she entered the water from a 40m slide, the ABC reports.

Paramedics tried to revive them both but they were pronounced dead at the scene.

"With the boy we have no information to indicate he was on the slide but that's what we hope to uncover," Inspector Campbell said.

Adam Cini said learning of his sister's death made for the worst day of his life.

"I will never see my beautiful baby sister again," he posted on Instagram on Saturday.

"I have experienced so much pain in my life but nothing knocks me down like this, I am so lost now."

The pair were earlier partying at a "typical Australia Day event," Queensland police spokesman Duane Amos told the Seven Network.

"Everyone's enjoying themselves, unfortunately there's alcohol that's mixed with water and we have the tragic (deaths)," he said.

An investigation into the circumstances has been launched.