buoyant mass center

Hej Guys,

I was wondering.. is it valid to calculate the buoyant mass center just as on the image? A hollow object hangs into the the water pool, I have a hard time to define what would be the buoyant volume of the object. So that the bending force would be equivalent to the water displaced, and the center of the force would be the center on the image? Even it would be valid to calculate torque on it?

Thx again!