I wondered about that, too. I assume they were part of cache that was "deep-sea disposed" but separated out, or never made it out to the correct disposal site, ("ah heck, this is probably far enough out...")
It’s weird. The only info I can find is that the police either didn’t respond to queries or,
“On Facebook, police said they could not confirm where the devices came from.”
There’s NOTHING on how these things ended up in the ocean. Even USA Today simply referenced the Newport Police. It’s like the media has been directed not to ask questions of the US Army (i.e., the ‘logical’ question and literal origin of the devices).
https://armypubs.army.mil/ProductMaps/PubForm/Details.aspx?PUB_ID=65134
Funny: I don’t recall the US Army operating in the Pacific Ocean. Again, I have to wonder what else they lost...