fluid properties-state of body in motion under the fluid surface Body is moving downwards in the fluid with uniform velocity.So, buoyant force = weight of the body. What will the state of the body represent:- sinking or submerged?
p.s:The doubt is regarding the definitions of 'sink' & 'submerged'states and their usage in the situation described above.
 A: The body is moving downward in a fluid with uniform velocity - it means that the net force on the body must be  zero.
the body is moving downward inside the fluid ,so it is "sinking " as time elapses and it can not be called submerged.
Now about forces operating on the body - the following are acting-


*

*the gravitational pull of the earth equal to (mass x acceleration due to gravity).

*The force of buoyancy provided by the liquid/fluid acting upwards opposite to the weight.

*The force of viscous drag  due to relative motion between layers of fluid and the contact surface of the body and this drag is /may be proportional to the velocity of the body and acts in a direction  opposed to the motion of the body- 
So it acts upward .The drag is also  proportional to coefficient of viscosity of the fluid.
Therefore the force equation for the moving body should be,
F(net)= mg -buoyant force - viscous drag= 0 .
A different conclusion from the  question given above :
The wt. of the body must be equal to sum of the buoyant force and viscous drag acting on the body.
The uniform speed is called "Terminal velocity".
This experiment is   Stoke's Experiment to find the coefficient of viscosity of the fluid.
