August at Nawiwili harbor -- protestors stop the Hawaii Superferry dead in its tracks.

"My legal advice to them would be don't go in the water," said Lanny Sinkin.

That's what the environmental activist and lawyer said he meant when he wrote a letter that found its way to The Surfer's Path, the Web site of popular surf magazine.

The letter warns Kauai protestors to anticipate law enforcement to "act without restraint" when the Superferry returns. It encourages them to prepare a will. It says to be ready at the level of the Native American who decided when it was "a good day to die."

"Losing your life is one of the possibilities," Sinkin said.

State Attorney General Mark Bennett said the letter encourages people to break the law.

Sinkin said he's asking them to count the consequences.

The Surfer's Path is a magazine big on environmental concerns. It has a circulation of 40,000 in the United States and United Kingdom.

The letter caught the FBI's attention.

"The FBI in collaboration with its partners over at the United States Coast Guard will investigate any threats to the Superferry operation," said special agent Brandon Simpson.

Sinkin wrote the letter with activist Jim Albertini.

Sinkin said they both agree the letter was meant to warn and not to encourage anarchy.

"Everybody has free will," Sinkin said. "If someone decides they're going to do something in order to make a statement that something is wrong and needs to be corrected, I say, bless them."

He said that's not the same as saying lay down your life.

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