Why does a bucket of water weighs less inside the well water?

(i) Explain, why a completely immersed bottle in water bounces back on the surface?
(ii) Why does a bucket of water weighs less inside the well water?

(i) Since, it is known that a body can sink in water only when its weight is greater than the upthrust act on it by the water. But in this case, the upthrust act on the bottle is greater than its weight, thats why, it bounces back on the water surface.
(ii) A bucket of water weighs less inside the well water, it is because when the bucket immersed in water fully, upthrust act on it by water which reduce its actual weight.