This is a wading stick, it's used by fisherman to test the depth of water as thay wade out into a river to fish. A wading stick is basically a thumb stick with a lanyard to tie the stick to your vest so that you don't loose it! Note also in the second photo the bottom is weighted to keep it from floating up off the river bed. A rubber ferrule is used on a wading stick so as not to make any noise that would scare away fish in the area.
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