Why do fish drift? I'm not asking about fishing skills, but I want to know the physics inside. Just like a densitometer, why not sink and stand upright?

Raw materials for making fish floats, such as plastics and wood, are less dense than water, so they can float on the water. The float is upright because it is still connected to the line group. When fishing and drifting, the buoyancy of the float should be balanced with the gravity of the line group, so as to be suspended in the water. At the same time, you can also observe that the center of gravity of the fish drift is generally low, which is convenient for "turning over", except for the seven-star drift.