A toddler died in hospital after almost drowning in a backyard pool that shouldn't have been in use at the time, a NSW coroner has found.

Jake Rhodes was 21 months old when he was found floating face down in a family friend’s pool in the NSW town of Pimlico in January 2015.

Deputy State Coroner Derek Lee handed down his inquest findings on Tuesday at Glebe Coroner’s Court noting Ballina Shire Council had yet to issue a final occupation certificate for the pool so no one should have been using it.

The inquest earlier heard the toddler had travelled with his father, Rodney Rhodes, and three siblings to stay with friend Danielle Forsythe on January 9.

A pool had been built at her Pimlico home the previous month with a temporary fence erected around it. Mr Rhodes agreed to help install a permanent fence when he visited.

The inquest heard conflicting evidence from Ms Forsythe and one of the builders, Shem Bragg, about what was said at the handover of the pool in December.

Ms Forsythe said she was of the belief the pool was ready for use, but Mr Bragg denied telling her she could use it before the final occupation certificate had been issued.

Regardless, the kids were swimming in the pool while the permanent fence was being constructed.

Mr Rhodes was working on the fence on January 16 when two of Ms Forsythe’s friends brought lunch over.

A short time later one of the adult’s spotted Jake’s body floating in the pool.

He was in cardiac arrest for about 90 minutes before his heart restarted and he was airlifted to Lady Cilento Children’s Hospital in Brisbane in a critical condition on a ventilator.

Scans found significant brain swelling consistent with brain death.

His family was given the opportunity to say goodbye and his ventilator was removed on January 17.

Mr Lee found the toddler had died from “misadventure”. The coroner on Tuesday recommended builders issue explicit written instructions that pools not be used until they are certified.

By David Sigston