Following his son and dog's lead, Guy jumped into the water to save Poppy, the youngest of the three who were dragged out to sea.
Nicola told Portsmouth.co.uk she went in to rescue the pair but got caught in trouble herself.
"I went into the water because the girls were in trouble screaming at me. By the time I got to both the girls Kiera had drifted away," she said.
"Poppy was in more trouble so I went to her but by the time I reached her she was panicking too much and started pulling me under too.
"Kiera wasn't panicking as much because she knew it would help to turn on her back and float, but Poppy was in terrible trouble.
"She was being dragged underwater and kept screaming, 'Mum! Mum! Help me!' But I just wasn't strong enough to do it.
"Both of us in the water thought our time was up."
That was until Guy, Tom and Dave came to the rescue.
"There was no bravery, it was just bang, straight in," Guy explained.
"Dave's our little hero and I'm proud of Tom."
Nicola said they wouldn't be alive today without the three heroes.
"We owe our lives to Guy, Tom and Dave and as the saying goes - not all heroes wear capes.
"I'll never be able to thank them enough. We're going to stay friends, and go on dog walks together."