(CNN) -- A day of kayaking and backpacking on Hawaii's Big Island changed in an instant as the might of the Pacific Ocean swept six teenagers into the surf.
One remains missing.
The group of 12 students and their guides, who were on their way to a waterfall, were taking a break at a tide pool 15 feet above the swirling ocean and 50 feet inland when rogue waves hit.
"(T)he waves were totally unexpected," Abbott Wallis, founder and executive director of tour operator Bold Earth Teen Adventures, said Sunday.
The surf sucked two of the teenagers into the sea Wednesday and left four others clinging for their lives along the cliff and rocky shoals.
Kayak guides "immediately dived into the water at risk to their own lives" and rescued five of the teens, said Bari Sims of Hawaii Pack and Paddle. The sixth, 15-year-old Tyler Madoff of White Plains, New York, has not been found. Authorities suspended search operations for his rescue Thursday evening.
The other student swept out to sea remains hospitalized after his rescue, but is expected to recover. One of the kayak guides resuscitated him at the scene.
"I can't convey my shock and sorrow," Wallis said. "We're doing all we can to support the families and students. As a parent myself, I can only imagine what the families are feeling right now."
Tyler's father, Michael Madoff, strongly criticized Bold Earth, but said the family would not seek legal action against the tour operator.
"People of Bold Earth Expeditions have shown poor judgment and extremely poor character," Madoff said Sunday. "None of the Bold Earth people stayed on site to continue the search for our son Tyler."
"We're devastated by this," Wallis said in response. "There's nothing Mr. Madoff can say that we disagree with."
A statement from the company says Bold Earth has served nearly 12,000 students on six continents since it was founded in 1976. Wallis said last week's accident was the first significant incident in the company's history.
CNN's Ed Payne contributed to this report.