This could as well be some organization's military machine that they're experimenting with. Just like how mysterious objects in the sky could be explained. It's actually the most logical explanation in most of these mysterious cases. This is explained well in the awesome recent documentary "Hypernormalisation". Check it out!
Why is that bizarre? It looks like a major passage to me. In a nuclear first strike scenario you want your nukes to be right at the front door so hopefully you can take out some silos before they launch. The militaries of the world have no doubt sprinkled hundreds of thousands of sea floor devices around the world since probably the 1950's. Some are probably nuclear powered, long since forgotten about, and will continue to emit for decades. There are fleets of autonomous ocean vehicles that go and gather their data and transmit it to satellites.
