I'm a caver, and involved in exploration. However, I'm not a diver. Frequently, while digging, we encounter a wet space, filled with rubble and water, that requires a dive or significant digging to be passable. In those cases, I'd like to be able to use a device to get a sense of width and direction, for sometimes the cave doubles back on itself. While that isn't immediately evident, the water moves in the right direction.
So I'd love to build a device that "follows the water" and can report back a series of datapoints to indicate the direction the water takes. I was thinking of something like a waterproofed semi-flexible "string" embedded with sensors that can relate left/right/up/down coordinates relative to the senor behind them, saved by waterproofed and ruggarized Arduino (perhaps stored within an Otter Box) to a small flash device.
While I can imagine the rig, I'd love thoughts and suggestions about which sensor(s) to use to accomplish this feat. After reading the forums, here's what I've learned:
(1) Some people have thought about calculating distance and direction by ultrasonic sound. This doesn't seem optimal, for caves are wet, noisy places. Likewise, if submerged, light isn't a good option.
(2) I see that there are semiflexible sensors (Flexibend) that output voltage changes based on "bend". This seems like a productive direction; we'd need a series of these sensors, and would also need some way to know more than "bend" alone. The "bend where" is important.
The ideal length would be about 20-30' and the line should be highly flexible and submersible. We don't need inch-by-inch granularity, but should have a good idea about the position/location each 12'' or thereabouts.