When military officials got word of the escape plans through intelligence operations, they sent Navy SEAL Team One on a rescue mission called Operation Thunderhead.
Dry commanded the team's Platoon Alpha, which was assigned to carry out the mission. He and about a dozen other SEALs headed to sea aboard a submarine, the USS Grayback.
Once close enough to the coast, Dry and other SEALs were to head for a small island off the mouth of the Red River in a mini-submarine attached to the larger ship, establish an observation post and watch for the escaped prisoners, according to Proceedings.
The SEALs never made it to the island. During a reconnaissance mission in preparation for the rescue, the mini-sub ran out of battery power shortly after midnight, and Dry and three other SEALs had to abandon it. They treaded water for eight hours several miles off the coast, according to Proceedings, until they were rescued by helicopter the next morning and taken to the command ship for Thunderhead.
Dry insisted on returning to the Grayback to help in the rescue mission. A helicopter carried Dry and the three other SEALs to the Grayback late in the evening of June 5.
The helicopter had trouble determining its altitude and finding the submerged submarine.
After a number of failed attempts, the helicopter crew thought that it spotted the submarine, and when Dry got the signal from a crewman, he jumped.
Treacherous jump
But the helicopter, caught in strong winds, was too high - about 40 to 50 feet, significantly higher than what was deemed safe for a jump, witnesses recounted.
Three others who jumped from the helicopter were injured. Dry's body was found that night. The Navy listed the cause of death as "severe trauma to the neck."
The rescue mission was eventually aborted, and officials later learned that the escape attempt had been called off.
The day after Navy Capt. Melvin H. Dry learned of his son's death, he wrote one word, "Desolation," in his diary. He was determined to learn more, meeting with officials and writing them.
Navy officials were vague about the circumstances of Dry's death, according to Proceedings, largely because they did not want word to get back to the North Vietnamese that an escape mission had been planned. Dry's father learned more about the mission little by little over the years, as information leaked out.
Captain Dry died in 1997. He and his son share a grave at Arlington National Cemetery in Virginia.
