It is part of the Global Sumud Flotilla, a group of dozens of boats carrying 500 people - including the Kiwis and Swedish climate campaigner Greta Thunberg - trying to break Israel's blockade.
Flotilla organisers said the boats of Rana Hamida, Youssef Sammour and New Zealand teenager Samuel Leason had been illegally intercepted.
Leason, from Otaki, posted to social media that it appeared his boat had come up to what was believed to be an Israeli military blockade.
"It looks like we're going to be illegally intercepted by Israel," he said in a video.
"If we made it through the night we will actually see the shores of Palestine, and I mean obviously there's still a chance that we might. We've a lot of ships here and it will be very difficult to stop all of us."
However, he said it would be the last post for a while "because I'm going to be in Israel".
The 18-year-old expressed concern for Sammour and Hamida, who are Palestinian-New Zealanders, saying he feared they would be "in a lot more danger than I am".
The Israel Foreign Ministry said the "sole purpose" of the flotilla - which it called the "Hamas-Sumud" flotilla, using the name of the group which launched the 2023 attacks which sparked the current fighting - was "provocation".
"Israel, Italy, Greece and the Latin Patriarchate of Jerusalem have all offered and continue to offer the flotilla a way to peacefully deliver any aid they might have to Gaza. The flotilla refused because they are not interested in aid, but in provocation.
"The Israeli Navy has reached out to the Hamas-Sumud flotilla and asked them to change course. Israel has informed the flotilla that it is approaching an active combat zone and violating a lawful naval blockade. Israel reiterated the offer to transfer any aid peacefully through safe channels to Gaza."
It also shared a video of what appeared to be an IDF soldier helping Thunberg put a jacket on.
Leason said it would be the last post he made for a while.
"Once we get back to New Zealand then, you know, the mahi starts again. But keep fighting fun and keep fighting for Palestine."
The flotilla has reportedly been under attack from drones in recent weeks.
The Israel Foreign Ministry said the passengers were safe and healthy and were being safely transferred to an Israeli port.
New Zealand's Ministry of Foreign Affairs and Trade (MFAT) told RNZ the embassy in Ankara, Türkiye, was in contact with the Israel Foreign Ministry in regards to consular services any New Zealanders might request.
"New Zealand has a long-standing 'do not travel' advisory in place for Gaza," a spokesperson said.
" The advisory explicitly warns New Zealanders against any attempt to enter Gaza by sea in breach of Israeli navy restrictions, including participation in flotillas to deliver aid."
Kiwis shouldn't travel to Gaza: PM
Prime Minister Christopher Luxon said he had seen the reports about the flotilla.
"That is why New Zealand has had a 'do not travel to Gaza' [advisory] for some time, by sea, by any means… It's been a pretty clear explanation for a long period of time.
"We have told the Israeli government that we expect them to be treated with respect to their obligations under international law. But also importantly, we'll offer consular assistance as needed in due course."
MFAT said it had told Israel "several times" it expected New Zealanders to be "treated in a manner consistent with international law".
It declined to comment on individual cases for privacy reasons.
Tens of thousands of Palestinians have been killed since Israel launched its retaliation for Hamas' 2023 attack, which killed about 1200 Israelis.
New Zealand at the weekend said it was not yet time to recognise Palestine as an independent state.
Dad 'immensely proud'
Adi Leason told RNZ's Midday Report programme today he last spoke with his son on Wednesday night.
"He's been quite calm and focused, just giving us sort of the bullet points of the updates. They had a submarine that had surfaced and was circling the flotilla. There were other vessels in the distance that were part of the naval blockade preventing supplies landing on the beach."
He said the flotilla leadership assured participants the Israeli navy had told them they were not going to be attacked and sunk, so "that was reassuring".
However, communications with the group were now lost.
"The pattern has been with other boats... everyone just gets taken aboard a military vessel and over the over the the course of today, probably as we speak, that boat will be loading activists and doctors and journalists and then taking them back to be incarcerated somewhere in one of the big detention centres in Israel."
From there, he expected deportation would happen "pretty quickly".
"There's an immediate deportation - some activists are choosing to not comply with the process and are remaining in custody a bit longer and forcing Israel to deport them. I think Samuel has indicated that he is prepared to take his struggle and his witness to sort of another level and stay in jail as, I guess, a silent witness."
He said it made him "immensely proud".
"We've been going to mass every Sunday for 18 years with Samuel, and he must have been listening and taking something of that formation on board. It's lovely to see a young man with a deep conscience curing so deeply about people who he will never meet and to put himself in harm's way for them."
