I would imagine some Navy ships would have compact ionospheric heaters on board for strategic purposes. Some of the sightings are happening over Navy ships.

In fact, one of the ideas I pondered which could explain these UFOs, is a type of light or laser that could produce a signature which looks like a physical object, but isn't, somewhat like a hologram or several light beams being triangulated in the air. Light phenomena could definitely explain their characteristics such as rapid acceleration, incredible speed, disappearing into water, etc. Light can do all of this easily.

But I think it's military playing with toys, testing other toys, without either team knowing exactly what's going on. One team tries to evade with some novel tech, while the other team tries to detect it with some existing tech. Maybe skunkworks.

On another front, perhaps there are pure light beings out there.