Eight-year-old Ross Parry on how assistance dog Paddy helped rescue him from possible drowning at Thorndon Pool in Wellington.

Nobody noticed eight-year-old Ross Parry was in danger of drowning at Wellington's Thorndon Pool – except for Paddy the black labrador.

Liz Gasson's assistance dog, who helps her cope with multiple sclerosis, knew something was wrong, and became agitated as she sat beside the pool reading a book on Monday.

"All of a sudden, he pulled forward, and then he sort of started nudging me towards the direction of where the little boy was," Gasson said.

ROSA WOODS/STUFF Our hero: Paddy with, from left, Johnathan Gasson, Liz Gasson, Rhianna Parry, Anita Downey Parry, and Ross Parry.

Gasson said Ross had tried to use his leg as a lever to get out of the pool, but instead his foot became lodged in a handrail.

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"It was an immediate response. [Paddy] just immediately got up and realised something wasn't right ... it was amazing. I'm so proud of him," Gasson said.

ROSA WOODS/STUFF Ross and Paddy back at Thorndon Pool on Tuesday. "He's a superhero," Ross says.

Ross was lying backwards in the water, struggling to keep his head above the surface.

His sister Rhianna was calling out for help, trying to alert the pool's lifeguards, who had been dealing with a group of rowdy children.

Thanks to Paddy's attentiveness, Gasson and her husband, alongside Ross' mum Anita, freed the boy's leg and lifted Ross safely out of the water.

ROSA WOODS/STUFF Paddy noticed Ross was in trouble, and struggling to keep his head above water. He alerted his owner, Liz Gasson, who rushed to help, along with her husband and Ross' mum, Anita.

But Paddy's work wasn't over yet.

After the successful rescue, he consoled and calmed Ross the only way he knows – by licking his face.

Ross had swallowed a lot of water, and admitted "it was really scary".

But he insists the incident wasn't all bad, as he had found himself a new best friend.

"He's a superhero," Ross said.

Paddy, who turns three in March, was born on St Patrick's Day, with Gasson referring to him as her "little lucky charm."

"He's just an amazing dog. He knew something was going on far before anyone started shouting or anything like that.

"If it wasn't for Paddy alerting me, the kid would've been underwater longer.

"It was quite extraordinary. He was the first to recognise that something wasn't right.

"It could have been potentially very dangerous."

Paddy's extensive training as an assistance dog ensures Gasson has the freedom to live as normal a life as possible.

Assistance Dogs New Zealand was founded in 2008 to provide support for people with disabilities such as autism, Down syndrome, cerebral palsy and diabetes.

Paddy's training cost about $48,000.