Samoan police believe a New Zealand Navy sailor who has been missing in Samoa for more than a week may have fallen into the sea and been swept away.

Kilino Joseph Lemafo'e Tua, 24, who grew up in Mangere, Auckland, was visiting two of his uncles, who live near Apia on Upolu Island, when he disappeared last Saturday - a day after he arrived in the island nation.

He left his uncle's house to go exploring on the morning of April 29.

Tua's car was found parked near the famous tourist spot and swimming hole of To Sua Trench that day.

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Police are continuing to investigate Tua's disappearance and are doing their best to recover his body, Samoan police spokesman Su'a LeMamea Tiumalu told the Samoan Observer.

"We suspect that he either fell into the ocean or he was struck by a wave. "On the day of the incident, the sea was very rough," he said.

A spokeswoman for To Sua told the Samoan Observer that To Sua staff agree with the police's theory that Tua was likely at the trench enjoying the view and the scenery when he got in trouble.

Earlier this week police were investigating whether Tua may have drowned in the trench, but they've now ruled out that theory.

"We will probably have to scale down the numbers but I can confirm that the police are still looking for the young man," Tiumalu said.

Meanwhile, Tua's family continue their desperate search to find out what happened to their loved one.

Two of Tua's siblings travelled to Samoa with their parents this week.

His sister Isabel Tua yesterday told the Herald searchers had found Tua's bag, hat, iPad, wallet and passport near To-Sua Trench and the family was coming to terms with the thought Tua may have died, and were now hoping to recover his body.

They had logged into his Snapchat account and were searching through his recent photos to see if they could find any clues what had happened to the former De La Salle College student.

"It was from Saturday morning," Isabel Tua said of the last social media post.

"It was a beautiful day and you could see the sun shining."

The family have declined to share the image publicly.

The New Zealand High Commission in Apia is assisting Tua's family, and the New Zealand Navy had sent a family liaison officer to Samoa.