Rumbles

Sometimes, I can hear a deep rumble at night when I am trying to sleep. It comes during the witching hours from above the land, and sea. From the sky. It cannot be felt through water, nor the vibrations felt behind glass. It is sound, entirely. Unknown origin.

I assumed it was a human contraption. A plane, a helicopter, drone, engineering I don't quite understand but recognize the sound of. It belongs to none of those things. It's unlike anything I've ever heard.

It does not come every night, but always around the same time when it does. It sounds like it's hovering over me, and lasts for minutes at a time, before quietly fading away. I've tried to look for the source, but to no avail.

I rise my head above the waters each time and it still remains unseen. Even on clear skies it remains invisible. If I had to guess, some form of helicopter with the lights turned off or simply in a direction too far away for me to see. But it really sounds more like it's been put underwater. Whatever its business is, who knows...

No, I do not believe it is an alien ship or "UFO".

I highly doubt that would go unnoticed multiples times, ignoring that I don't believe science-fiction depictions of aliens are even remotely accurate to what an extraterrestrial being's airspace vehicle would look or sound like (we have no idea what they would even be). But it does sound "alien".

I've been keep track of what I note about the sound:

It is only heard on clear nights

It cannot be seen

It does not make the water ripple

It is from the sky

It hovers for minutes at a time

It sounds like it's in front of me, direction-wise

It does not sound like any specific vehicle or device

Description, via chromesthesia:

Flashing grey rectangles with fuzzy edges, long in width but short in height, arranged in a pattern of a larger rectangle, partially overlapping

Comparison to a helicopter: From left to right, a grey ovular dot in a sideways cone that narrows to a point going right, also grey, flashing and repeating in a counter-clockwise motion only visible from 20:00-22:00 hours, leaves a fuzzy afterimage

I have a tendency to personify it... I enjoy personification, and all that.
I like to think it is searching for something, at night when all are asleep. I think it waits along the forests and lakes and roads, collecting data, hoping to find what it is looking for. Across the water, however... I don't think it's considered that. Whatever it wants is clearly not in any body of water, lake or ocean. I imagine it must be a land-based creature then. Or perhaps a robot that can't touch water, who knows.

I think it's best to leave it alone. Pretend to be asleep. Do not leave the safety of the den. It will not bother you.

I wonder if it has a pilot? Realistically it does... or perhaps it's one of those anthropomorphized planes from animated movies. That would be really funny to think... maybe it has big googly eyes.

Anyways, it's hard to say what it is... I'm not afraid of it exactly. It does make me anxious to think about, when I poke my head above the water. But as long as it means no harm, and it hasn't hurt anyone, I'll consider it another curious part of the world that goes unexplained. One of life's many great mysteries.

I look forward to hearing it again.