Eventually a wave "ripped Albert from his arms, forcing him to let him go and concentrate on saving Lucile''.
Mr Wilson said it took him five minutes to reach the struggling pair but 15 minutes for a rescue boat to eventually pluck Ms Fruean from the water.
He told the coroner he was disappointed by the time it took surf lifesavers to get to him and said he believed Mr Alapati may have survived if he'd been reached sooner.
However, the group was not swimming between the flags erected by the Titahi Bay Surf Life Saving Club, where five lifeguards were on duty.
"I don't know how much more I could have done,'' Mr Wilson told the coroner.
"The last time I got dragged under was when I couldn't hold on to the boy anymore.
"It was a case of lose one to save myself and the girl.
"I just did what I had to do.''
Mr Evans said: "It is plain to see that Lucile owes her life to Mr Wilson, whose valiant endeavours to save Albert's life were thwarted by the exceptional sea conditions prevailing at the time.''
The coroner heard evidence that Ms Fruean's mother had told Albert and his younger brother, Sae, they were not to go swimming on that afternoon.
The evidence was that Mr Alapati, Ms Fruean and their siblings were "just paddling around in the water and playing in the waves that were coming in'' before they were caught by the rip.
A surf lifesaving official told the coroner no one was swimming between the flags when the group entered the water. None of the lifeguards on duty had seen them.
Mr Evans found no one responsible for Mr Alapati's accidental drowning.
The coroner recommended a sign be erected "as soon as possible'' at the northern and southern ends of Titahi Bay Beach warning of the dangers of rips.
