Two versions:

132 Cong.Rec. S3564-02
AMENDMENT NO. 1718
(Purpose: To restrict assistance to the Nicaraguan democratic resistance to
humanitarian assistance, and for other purposes)

Finally, President Nixon, 1970. "In cooperation with the armed forces of South Vietnam, attacks are being launched this week to clear out major enemy sanctuaries on the Cambodian-Vietnam border."

Mr. President, I remember Christmas of 1968 sitting on a gunboat in Cambodia. I remember what it was like to be shot at by Vietnamese and Khmer Rouge and Cambodians, and have the President of the United States telling the American people that I was not there; the troops were not in Cambodia.

I have that memory which is seared--seared--in me, that says to me, before we send another generation into harm's way we have a responsibility in the U.S. Senate to go the last step, to make the best effort possible in order to avoid that kind of conflict.

From the Boston Globe:

The Christmas Eve truce of 1968 was three minutes old when mortar fire exploded around John Forbes Kerry and his five-man crew on a 50-foot aluminum boat near Cambodia. ''Where is the enemy?'' a crewmate shouted.

In the distance, an elderly man was tending his water buffalo -- and serving as human cover for a dozen Viet Cong manning a machine-gun nest.

"Open fire; let's take 'em," Kerry ordered, according to his second-in-command, James Wasser of Illinois. Wasser blasted away with his M-60, hitting the old man, who slumped into the water, presumably dead. With a clear path to the enemy, the fusillade from Kerry's Navy boat, backed by a pair of other small vessels, silenced the machine-gun nest.

When it was over, the Viet Cong were dead, wounded, or on the run. A civilian apparently was killed, and two South Vietnamese allies who had alerted Kerry's crew to the enemy were either wounded or killed.

On the same night, Kerry and his crew had come within a half-inch of being killed by "friendly fire," when some South Vietnamese allies launched several rounds into the river to celebrate the holiday.

To top it off, Kerry said, he had gone several miles inside Cambodia, which theoretically was off limits, prompting Kerry to send a sarcastic message to his superiors that he was writing from the Navy's "most inland" unit.

Back at his base, a weary, disconsolate Kerry sat at his typewriter, as he often did, and poured out his grief. "You hope that they'll courtmartial you or something because that would make sense," Kerry typed that night. He would later recall using court-martial as "a joke," because nothing made sense to him -- the war policy, the deaths, and his presence in the middle of it all.

This is only two versions. There seem to be several more. Thanks to one of many sources still looking into this while the press looks firmly in the other direction.