Hi Elsie,
Sorry to let the wind out of your sails but check my posts in these threads

http://www.poolforum.com/pf2/showthread.php?t=101


http://www.poolforum.com/pf2/showthread.php?t=561

What I found is even turbulence due to sun heating can be a problem. When I did the leak chasing I did it in the early part of the day before the sun started heating things up. Even moving the pole along the bottom causes turbulence. Slow and easy is the rule. Even fussed with trying to build an electronic detector but didn't get anywhere and finding the blasted leak by any means was a priority. I've also suggested several time that beets are a good, cheap, harmless dye source. Chop up raw beets, boil, and use the red water. Then eat the beets.
Hey, if you can come up with a patentable idea go for it.

Al