A body of mas m is being emerging into the pond of water of depth h, how long will it take to reach the bottom

a body of mas m is being emerging into the pond of water of depth h, how long will it take to reach the bottom

Depends on a couple of other factors besides just mass. First, you need to know the volume of the body so as to determine the buoyancy force of the displaced water. And if this problem is for an advanced class in fluid mechanics where you're studying topics such as viscosity and Reynolds number, determining the coefficient of friction (which controls the amount of drag presented by the water) can be complicated.