The Kerry campaign took it's recitation of this action off its website, not long ago. ....
Here is what is used to say (as of April, anyway - the Boston Globe, Kranish of all people, called Kerry out on this one) ...
-- Kerry 1969 Vietnam Action
The following is a summary of combat actions of PCF94 from Jan 1 to March 17, 1969 taken from after-action reports and the Coastal Division Eleven Command History on file at the Naval Operational Archives. All locations are near the south end of the Mekong Delta in Vietnam.
26 JAN 1969 Ong Doc River
PCFs 94 and 66 escorted troops up the Ong Doc River early in the morning when they were ambushed by gun and rocket fire from approximately 40 men on both sides of the river. Two B-40 rounds hit close to Kerry's boat, while PCF 66 received 2 B-40 rocket hits. Three men on PCF66 were wounded. A junk containing South Vietnamese troops was also sunk, killing 11 South Vietnamese troops. Intelligence reports after the mission indicated that the Viet Cong troops may have planned the ambush in advance.
27 JAN 1969 Cua Lon and Dam Doi Rivers
Five swift boats conducted operations in the Cua Lon and Dam Doi Rivers. The units received hostile fire twice during the operation.
29 JAN 1969 Cua Lon Rivers
Early in the morning seven swift boats embarked on a mission to destroy enemy installations along the Cua Lon River. While Kerry's boat and another (PCF72) were probing a canal along the river, Kerry's boat came under heavy fire and was hit by a B-40 rocket in the cabin area. One member of Kerry's crew -- Forward Gunner David Alston - suffered shrapnel wounds in his head. His injuries were not considered serious and he was sent to the 29th Evac Hospital at Binh Thuy.
Discrepancies noted in Kerry's record <-- Link
I know this is only tangential to the Alston question. I agree with others that Alston may have been under Kerry's command at some point, although the record does not clearly show that. We know too little to draw any conclusion, except, we do know that Kerry was not present when Alston got his head wound.