Key Points and Summary: In May 1969, the U.S. Navy’s nuclear-powered attack submarine USS Guitarro sank at Mare Island Naval Shipyard in California due to a series of preventable errors and miscommunications among civilian and Navy teams.
-While one group was filling the forward ballast tanks with water, another was draining the aft tanks—unaware of each other’s actions.
-Additional mishaps, such as the unsealed manhole cover for the submarine’s sonar dome, allowed water to flood critical compartments, ultimately causing the sub to settle on the riverbed.
-Though no lives were lost, the extensive damage cost the Navy $15.2 million and delayed Guitarro’s commissioning by three years.
“USS Guitarro: How Miscommunication Sank a Nuclear Submarine”
On May 15, 1969, the USS Guitarro, an American nuclear-powered attack submarine, sank while at Mare Island Naval Shipyard in Vallejo, California, as a result of a series of miscommunications and procedural errors by civilian and naval personnel working aboard.
The submarine, partially flooded during equipment calibration and ballast adjustments, tipped into the Napa River, taking on enough water to sink to the riverbed. Although there were thankfully no injuries nor fatalities, the accident caused a great deal of damage, necessitating millions of dollars of repairs and postponing the Guitarro’s entry into service for several years.
A Lost Nuclear Attack Submarine: A Series of Mishaps
A series of avoidable mistakes caused the sinking.
On the day of the accident, two teams were working on the submarine, but each team was unaware of the other’s actions.
One team was calibrating the submarine’s forward ballast tanks, filling them with water, while another team was conducting tests in the aft ballast tanks, removing water.
Inexplicably, neither team had coordinated or communicated with the other.
The submarine’s buoyancy became precarious, and it eventually listed significantly. Attempts to pump water out of the submarine failed, and the submarine ultimately sank.
The official account of the submarine’s sinking explains that in addition to negligence on the part of the contractors and workers on the submarine, necessary safety precautions on the submarine had not been taken:
“In the most forward part of the ship is the bow structure sonar dome which contains the ship’s sonar sphere. Entrance to the dome is through a manhole which has a bolted cover. At the time of launch, this opening was also protected by a cofferdam approximately three and a half feet high. This additional precaution was taken to make sure that occasional water did not run down onto the electronic gear which was exposed at that time.”
The sonar’s operation is dependent on a number of large electronic components known as transducers. Sometime after the sonar equipment was installed it was discovered that some of these components were faulty and would have to be replaced. To facilitate this work, the cofferdam and the bolted manhole cover were removed. This occurred in early March 1969 and neither the cofferdam nor the cover was ever replaced. At the time the Guitarro went down, the manhole cover was on the dock and the cofferdam was in the storage warehouse.
From the testimony and records before the Subcommittee, it can be reasonably concluded that on May 15 a simultaneous trimming operation and calibrating test caused a sufficient change in the Guitarro’s draft to permit water to enter in quantity through the open sonar dome manhole. As the sonar dome became flooded, its weight caused the ship to further settle by the bow which permitted additional water to enter other openings. This soon allowed massive flooding through the large bow access and at this point the Guitarro was doomed.”
A Sad Day the U.S. Navy Nuclear Submarine Force
This accident was exacerbated by a lack of communication protocols between groups.

USS Sunfish SSN-649. Sturgeon-Class Submarine.
Civilian contractors and Navy personnel had similar tasks and responsibilities that day but did not establish a clear channel of communication and coordination.
The Guitarro accident exposed shortcomings in the Navy’s management system and resulted in better oversight and reformed Navy yard operations.
Aftermath
The Guitarro remained submerged in the river for several days after it sank, though the Navy ultimately refloated the Guitarro at great expense.
The submarine’s refloat and repairs ultimately cost the Navy an estimated $15.2 million — at the time, an enormous sum. The mishap delayed the Guitarro’s commissioning by three years when it entered service in 1973.

Sturgeon-Class submarine. Image Credit: Creative Commons.
Despite its inauspicious start, the Guitarro went on to have an important career within the U.S. Navy. In its later years, the submarine was used as a testbed for the development of Tomahawk cruise missiles.
About the Author: Caleb Larson
Caleb Larson is an American multiformat journalist based in Berlin, Germany. His work covers the intersection of conflict and society, focusing on American foreign policy and European security. He has reported from Germany, Russia, and the United States. Most recently, he covered the war in Ukraine, reporting extensively on the war’s shifting battle lines from Donbas and writing on the war’s civilian and humanitarian toll. Previously, he worked as a Defense Reporter for POLITICO Europe. You can follow his latest work on X.
