Apply overlay effect in an area just on specific objects (2D underwater)

Hi, I would like to apply in an area, an overlay effect on specific objects (Sprites).

The desired effect is in the image below: when the barrels enter in the water, part or all of the image are affected by the effect.

The other objects of the scene are not changed, like the seaweed and rocks.

So how can I do this? Using stencil shaders? Any idea?