The Santa Cruz County Sheriff's Office said a bomb, covered in barnacles and sea debris, was found washed up on a nearby beach after recent storms and "was determined to be an inert military ordinance" by its bomb disposal team, Newsweek reported Tuesday.
The Santa Cruz County Sheriff's Office also said Travis Air Force Base, near San Francisco, sent a team to collect it for disposal.
It is not known in what potential battles it could have been deployed, as experts cannot yet determine from what time period the bomb originated or which nation built it.
Although coming across unexploded ordinances is common in areas such as Europe, which was subject to intense aerial bombardment during World War II, it is relatively rare for bombs to turn up on American shores.
For example, in Britain, unexploded ordinances from the Nazi blitz are regularly found in waterways such as the River Thames in London, and, this past year, munitions from both world wars were found in the river in Oxford, according to Newsweek.
The British government estimated in a 2020 report there were half a million unexploded munitions weighing a combined 100,000 tons in the waters surrounding the U.K.