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The only instrument we have to guide us is a dive computer.
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Implied, but just want to confirm: The sole source of feedback to you that allowed you to hold a stop within +/-.1m was the computer's display? I mean, you might have used your eyes and ears as other "instruments" to watch particulate in the water and feel pressure changes. Just want to make sure I understand.
I have a Shearwater Petrel, and I suspect it samples depth at a rate of something like once per second. By the time the display shows I am one foot (yeah, Imperial units--feet--are shown to zero decimal places) beyond my target depth, my depth may already be accelerating closer to two feet.