In 1969, Cannon was assigned to Team One for the SEALAB III project, which would take place off San Clemente Island. He was one of four members of Team One assigned to open and secure the habitat, alongside fellow aquanauts Robert A. Barth, Richard Blackburn and John Reaves. On February 16, 1969, the SEALAB III habitat sprang a leak. Cannon, Barth, Blackburn and Reaves were twice sent down to SEALAB in the Personnel Transfer Capsule (PTC) in an attempt to repair the problem.[9][15]
Shortly after 0500 hours on February 17, Cannon began to convulse while working on the exterior of the habitat. Barth tried to save him, holding his head in the breathable gas pocket of the skirt surrounding SEALAB's entrance and unsuccessfully attempting to force the mouthpiece of the emergency aqua-lungregulator between Cannon's teeth. Finally, Barth dragged Cannon back toward the PTC, where his fellow aquanauts helped him bring Cannon inside and Reaves and Blackburn attempted resuscitation.[2][16][17] When the PTC reached the surface it was obvious that Cannon was dead. His body was placed in the outer airlock of the deck decompression chamber (DDC), returned to surface pressure and brought to San Diego Naval Hospital.[2][18] Cannon's funeral was held at Humphrey Mortuary in Chula Vista, California, on February 19. He was buried at Wacahoota Baptist Cemeteryincentral Florida.[5]
It was widely reported in the news media that Cannon had died of a heart attack.[2] However, the official board of inquiry, held in San Diego from February 28 to March 12, 1969, concluded that Cannon had in fact died of carbon dioxide poisoning. The carbon dioxide-scrubbing baralyme canister on Cannon's Mark IX diving rig was empty. The SEALAB III aquanauts, including Cannon, did not set up their own diving rigs. The identity of the person who failed to refill the baralyme canister was never determined.[2] SEALAB medical officerPaul G. Linweaver later suggested that Cannon would have realized his equipment was faulty had he not been suffering from extreme cold due to breathing pressurized helium.[19] Surgeon commander John Rawlins, a Royal Navy medical officer assigned to the project, also suggested that hypothermia was a contributing factor.[20]
According to John Piña Craven, the U.S. Navy's head of the Deep Submergence Systems Project of which SEALAB was a part, SEALAB III had been "plagued with strange failures at the very start of operations". According to Craven, while the other divers were undergoing the weeklong decompression, repeated attempts were made to sabotage their air supply by someone aboard the command barge. Eventually, a guard was posted on the decompression chamber and the men were recovered safely. A potentially unstable suspect was identified by the staff psychiatrist but the culprit was never prosecuted. Craven suggests this may have been done to spare the Navy bad press so soon after the USS Pueblo incident.[21] As a result, it has been suggested that Cannon's death was a murder.[22]
Cannon was married to Mary Lou Cannon and had three sons.[5][23] He was known for seldom complaining if his complaint would go against command authority.[2] He enjoyed reading the works of Zane Grey.[7]
^Radloff, Roland; Helmreich, Robert (1968). Groups Under Stress: Psychological Research in SEALAB II. New York: Appleton-Century-Crofts. ISBN0-89197-191-2.
^Hollien, Harry; Thompson, Carl L.; Cannon, Berry (1973). "Speech Intelligibility as a Function of Ambient Pressure and HeO2 Atmosphere". Aerospace Medicine. 44 (3): 249–253. PMID4690449.
