Agreed.
However (you knew there was a "however," otherwise why would I post), it is within the realm of possibility.
If you don't think that it is look up Dionisio Pulido.
I'll grant you, unlikely, particularly undetected (kinda hard to hide, even underwater) but still, possible.
Dionisio Pulido. That's the couple whose cornfield became the Paricutin volcano in one afternoon.
I would hope the USN checked out the geology of the mountain in question.