When the mug is kept in water there is no action of buyont force on the mug. so we feel lighter when kept in water. when it is taken up there is some pressure that acts on the mug so we feel hevier when removed from water.

3 4 3
When a mug full of water is kepi inside the water  feels lighter because water is also applying a force on the mug ie the buoyant force
3 2 3