This is a bit off topic, but could you attach a camera to an anchor?
I'm watching "Sailing La Vagabonde" and they say they they always dive to see if their anchor is properly set. Nothing fancy, just an action camera / go pro with a power cable and some HDMI cable going to the input of some monitor could work if you can make it watertight. So unlike the test video linked earlier in the thread a camera that stays permanently attached to an anchor and is powered "from above" to check on it. Probably cable length would become a problem.
EDIT: Thinking about this a bit some
PoE underwater camera (power over internet IP camera) would do for this.
I've also had this idea of an underwater camera, like an underwater drone that you can rotate around and turn on a light. Kind of like an inverse periscope that allows you to marvel at the underwater landscape on a 4k monitor. Of course that is even more involved but with 3D printing and cheap servos and arduino these things become somewhat easier to make now (still lots of work of course). You'd need some kind of glass sphere to put the camera and the rotating jig in and seal it watertight. Maybe the glass from an outdoor lamp would do plus a 3D printed / manufactured lid.
But how would you fix it to an anchor and deal with the anchor chain and a long cable? Maybe makes no sense to combine the two ideas into one thing.
I'm a total newbie and my dream of cruising around on my own boat is still far off, but any thoughts on this? I bet this already exists in some form or another.