Berry Louis Cannon (March 22, 1935 – February 17, 1969)[1][2][3] was an American aquanaut who served on the SEALAB II and III projects of the United States Navy.

[7][8][9] Cannon was a civilian electronics engineer at the U.S. Navy Mine Defense Laboratory in Panama City, Florida, where he designed intercommunications systems.

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.

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-lung regulator between Cannon's teeth.

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] 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.

[2] SEALAB medical officer Paul 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.

[20] Surgeon commander John Rawlins, a Royal Navy medical officer assigned to the project, also suggested that hypothermia was a contributing factor.