SSN 665 History

On 15 May 1969, Guitarro was moored in the Napa River at Mare Island Naval Shipyard while construction was still underway. At about 16:00, a civilian nuclear construction group began to calibrate the aft ballast tanks, which required them to fill the tanks with approximately 5 short tons (4.5 t) of water. Within 30 minutes, a different, non-nuclear civilian construction group began an assignment to bring Guitarro within a half-degree of trim; this entailed adding water to the forward ballast tanks to overcome a reported two-degree up-bow attitude. Until shortly before 20:00, both groups continued to add water, unaware of each other's activities.^[1]

Twice between 16:30 and 20:00, a security watch advised the non-nuclear group that Guitarro was riding so low forward that the 1.5-foot-high (0.46 m) wakes of boats operating in the Napa River were sloshing into the sonar dome manhole, but the group ignored the warnings. At 19:45, the non-nuclear group stopped adding water to the ballast tanks and began to halt work for their meal break, leaving at 20:00. At 19:50, the nuclear group completed their calibrations and began to empty the tanks aft.^[1]

At 20:30, both the nuclear group, still aboard, and the non-nuclear group, returning from their break, noticed Guitarro taking a sudden down angle which put the forward hatches underwater. Massive flooding took place through several large open hatches. Efforts between 20:30 and 20:45 to close watertight doors and hatches were largely unsuccessful because lines and cables ran through the doors and hatches, preventing them from closing. At 20:55, Guitarro sank, leaving only her sail above water, earning her the nickname "Mare Island Mud Puppy".^[1]