questionsi found a fish finder watch, can i do anything…

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I'd start at hackaday. If you can't something that someone has done similar, the peeps in the forum should be able to point you in the right direction or give you some tips to get you going.

vote-for1vote-against

No, not really. It sounds like you have exhausted all avenues as to it's usefulness. Maybe find a replacement bobber somewhere?