Pond survey camera suggestions?

kelpdiver wrote:

https://www.bhphotovideo.com/c/buy/rovs/ci/25733/N/3877484839 - drones as low at 500, though with murky pond water, hard to know in advance if bright or dim lights are better. Better to borrow. Else, adjustable light power is an essential.

Wow. I had no idea you could get something like that for $500! Well, could if the $500 one was in stock.... That's probably the way to go.

When I built the ponds, I actually had the foresight to bury contacts under the liner so that I could measure resistance and from that deduce where a leak was, but the ground-level tops of those are not all intact 15 years later.

The expected leak is literally one or more chunks of liner missing thanks to a beaver. I had one piece of liner that is perhaps 2'x1' turn up on the shore... so I figure it came from somewhere. The soil under the pond has good clay content, but the pond does lie in a fold between two different rock types. A slow leak + evaporation would explain it all.

Kentucky is famous for it's limestone caves, and porous rock is under most of the area. Here's a satellite image of the area, my two ponds are the ones next to each other:

Rather famously, the big failed lake on the far left was 20' deep until one night about 25 years ago, when it literally emptied overnight. The failed pond to the right would be much larger if it filled (and the fence to my property would be underwater near the middle of it), but it has an average depth now of less than two feet (it's unusually high in this photo). In case you're wondering why I was foolish enough to build my two ponds between two failed ponds, the answer is that the upper one of mine was a swampy pond used to water cattle for 200 years, so I figured it was a pretty safe bet it would continue to hold at least some water... I always knew the lower one would be more of a risk, although it is still quite healthy despite the drop in level.

Both my ponds are fed entirely by runoff, and most of the runoff goes to the upper pond (to the right) and then overflows through a constructed waterfall into the lower -- so the lower pond naturally has a lot of level fluctuation. Unlike the upper pond, which has a small shallow area in the upper right and gets a fair amount of leaf litter, the lower pond has no shallows and just gets occasional branches in it from storms. Both my ponds should be 12' deep, and the upper one holds close to that, but the lower one has slowly dropped it's average depth from about 11' to more like 8' over a period of about 15 years; of course, level fluctuates a lot, with it still hitting 11' several times a year. Incidentally, there's a healthy population of sunfish and largemouth bass in each pond, and I've caught 6-pound bass in each.

BTW, if anybody has any suggestion for how to get a natural shoreline over the liner when the water level is fluctuating so much, I'd love to hear them....