The supporting force exerted by a fluid on an object immersed in it is called

buoyant force

Explanation:

The buoyant force is the pressure that is exerted on a immersed object by the surrounding fluid.  

The buoyant force acts on the surface of the solid object even if the object is immersed in the fluid partially or completely. If the object is immersed in a fluid, the net force is given by the formula:

where Patm is the atmospheric pressure at the top of the object

pgh = pressure of the part  in the fluid

F(bottom) is the upward force on the object

The net force is the same as the wight of the displaced object.

The principle is known as the Archimedes principle as the buoyant force is equals the weight of the fluid displaced by the object.  

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