(CNN) When the heavy rainstorms hit the Hawaiian island of Kauai, teams of volunteers climbed into their boats and got to work, rescuing those who found themselves trapped.

But some of those rescued said they were the victims of a scam when they were told to either pay or be left stranded.

Kauai Police said Friday those complaints led them to arrest boat operator Stephen Koehne, 33, on suspicion of extortion, robbery and terroristic threatening. He has not been formally charged.

Koehne's passengers were under the impression that he was ferrying them to a safer place, officials said. But when he made it approximately 200 yards offshore, he allegedly would demand money.

"Two hundred bucks a head, cash or credit, or we're going to leave you here," Kauai County Prosecuting Attorney Justin Kollar said Koehne told the passengers.

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