The prisoners, including Air Force Colonel John A. Dramesi were planning to steal a boat and travel down the Red River to the Gulf of Tonkin.
His father, retired Navy Captain Melvin H. Dry, spent the rest of his life trying to learn the circumstances surrounding his son's death.
The plan was to launch the team at night from the submerged submarine in a Swimmer Delivery Vehicle (SDV) piloted by two UDT-11 operators and head for a small island off the mouth of the Red River.
During briefings with the pilots, Lt. Dry and Chief Warrant Officer (CWO) Philip L. "Moki" Martin emphasized the maximum limits for the drop were 20/20—20 feet of altitude at an airspeed of 20 knots, or an equivalent combination.
Several hours earlier, Grayback launched its second SDV but the team abandoned their mission when their air ran out; subsequently, they made an emergency free ascent to the surface.
With the likelihood of a successful prisoner escape by sea lessened by the recent U.S. mining of North Vietnam's ports and rivers, Operation Thunderhead was soon terminated.
Because the mission was classified, the Navy did not acknowledge Dry's death as a combat loss until February 2008, when he was posthumously awarded the Bronze Star for Valor.