A related description of the incident can be found here:

Kerry experienced his first intense combat action on Dec. 2, 1968, when he "semi-volunteered for, was semi-drafted" for a risky covert mission in which he essentially was supposed to "flush out" the enemy, using a little Boston Whaler named "Batman." A larger backup craft was called "Robin."

Unfortunately, Robin had engine trouble, and Batman's exit was delayed until the boats could depart in unison. The Batman crew encountered some Viet Cong, engaged in a firefight, and Kerry was slightly wounded on his arm, earning his first Purple Heart on his first day of serious action.

"It was not a very serious wound at all," recalled William Schachte, who oversaw the mission and went on to become a rear admiral.

On the other side, we have Pat Runyon's interview here.

Obviously, somebody's full of shit here. I don't see a reason for Schachte to lie. But I don't see any reason for Runyon to lie, either. On the gripping hand, Schachte is backed up by his superior officer, and Kerry's own writings claim that he did not come under fire until later, although Democrats have been parsing that comment to try and make that sound like something else.

Kerry supporters say that no critics of the Democratic presidential candidate ever were aboard a boat with him in combat.

First of all, this writes Steve Gardner out of existence, something that he has been correcting. Second, a lot of recent pro-Kerry testimony has been from guys in other boats, which seems to contradict the premise that only the guys in Kerry's boat are valid witnesses.

Who was in that other boat? Would the crew of "Robin" know something about this? Can one or two of the squadrons of reporters assigned to defend Kerry at all costs look into that question?