Bobber
/ˈbɑːbər/
Definition 1 of 2
Pro Tip 1/3Outdoor Activity
The term 'bobber' is often used in the context of fishing, a common outdoor leisure activity. 
While camping next to the lake, we used a bobber to catch fish.
Pro Tip 2/3Visual Cue
'Bobber' indicates action visually; it's a sign to the fisher that something is happening. 
Keep your eyes on the bobber for it might twitch any moment.
Pro Tip 3/3Patience Required
Using a 'bobber' requires patience, as waiting for the fish to bite can take time. 
He sat silently, staring at the bobber for an hour before it finally moved.