I saw a documentary on TV a few years back where some fellow had captured these same critters flying around the mouth of a sinkhole in Mexico that sky divers jump into.They were only seen after viewing the image, never with the human eye. This is for a specific reason due to the way cameras work. In other words, there are no critters at all, and here’s why.

As any winged object flies through the frame, the wing is moving up/down. Depending on the position of the object in the frame, the wingtip may be at anywhere along the movement from the top/bottom of a single flap.
A very fast shutter speed minimizes this so you get a crisp shot of a flying bird.

If the object moves across the image closer to the lens, it would fly by faster than if further away. Depending on how slow the shutter speed was, the object may move across the image area during a single frame or more. The more it gets dark out or the darker the main view of the image area, the slower the shutter.

Critters are regular insects or such that have been captured by the camera as they fly by. As they zip by, they are nothing more than a blurred streak (unless you pan the camera with their movement of course). If the wing beat of the object is greater than the shutter speed, you’ll see its wings higher/lower than the body as it moves across the screen in a constant flow. Since it’s just one object (a point if you may) its position between frames jumps so that where it was at the end of the previous frame is where it is at the start of the next. It moves across the image in the mean time. So, the blurs start/end with one another between each shot. They never overlap as would any creature with a length to it as it moves across the screen. It’s the camera effect we’re calling critters. They otherwise don’t exist.

The part about the tether got me thinking that it looks more like out-of-focus near stuff than 3 mile wide things. The crew did say it was debris floating nearby and with binocular eye-site, they’d be able to tell.

That big orb was so ‘thin’ that even passing in front of the tether the brightness of it would overwhelm it. If there’s a better image with color or something like that you could see more clearly, I’d like to see that!

Still, it sure does look like sperm flying around looking for an egg

This would be watchable were it not for the extremely loud and extremely annoying “background” music…. that effectively drowns-out the narration and pervades the entire documentary, from beginning-to-end.

yes agreed…how dense does a film maker need to be to put out a film edited by some novice clearly…my god man what a waste off hard work and money to have this end result, and the content looked interesting from what i could stand until i turned it off…JACKASSES

Wow.  I assumed all the complaints about the music was just an exageration.  Unwatchable.  Make that unlistenable.

Fortunately, this seems to be a rehashing of other, more professionally made, documentaries.  If there is any new info presented, I wouldn’t be able to pick it out from under the music. 
Disappointing.