Plastic bucket :
Weight of water (contained in it) down wards.
weight of bucket down wards
Pulling (upwards) force due to the hands of the person, directed upwards.
The force exerted by the person = weight of bucket + weight of water
since the three forces are balanced, the net force is zero on the bucket. Hence, the bucket does not move and is in static equilibrium. or state of static inertia.
This is as per the first law of motion of Newton.