So you were in a boat over the deep spot, you let the washer to the bottom, fixed the slip bobber at the water level when washer was at the bottom or something similar and then went back to shore and measured the line? If so, that should be fairly accurate.
How old is the pond? when was it dug if you know?
Do you have a way to know how stable the water level is from season to season or do you have to live there a few years to sort this out?
Do you have access to water (well, or pump) and electricity nearby?
How did you determine no fish? Visual? Fishing? Maybe it is a new pond that you recently had dug?
I learned from this forum that nearly all existing bodies of water seem to have fish (lots of good discussion on whether source of these fish is spontaneous eruption, Darwinian process, mid air drop from kingfisher, friendly neighbors emptying their buckets, riding on duck feet, etc) Many have drained down their pond or used chemicals to kill fish and were surprised at what was found. Not questioning validity of your statement, just curious as how you knew.
Any forage for future fish? Leeches, bugs, crayfish, minnows, snails, etc? A minnow net (wire mesh) on the bottom with bait might be a very cool experiment.
Finding a big crayfish population might change your plans for future vegetation control, or finding existing minnows, or sunfish might change your stocking plans too.
