Seeking list of Merchant Marines ships during Vietnam

Looking for a list of ships used by the Merchant Marines during the Vietnam war, specifically the ones that entered the inland waters that dropped off supplies. I'm a Disabled American Veterans Chapter Service Officer assisting a former Merchant Marine Seaman that was on several tours to Vietnam duding the war, his ships entered the inland waters and unloaded supplies and munitions in the Southern region. He is also an Air Force Veteran that served state side duty after leaving the Merchant Marines. He has come down with several diseases associated with Agent Orange exposure. The Veterans Administration is requesting documentation that the ships he served on were in the inland waters of Vietnam during his trip dates. Any assistance will be greatly appreciated, Thank You!