What is the effect of pumping water out of the ballast tanks of a submarine?

Question

please answer soon

Answer 1

Water does not get pumped out of the main ballast tanks.  It gets blown, either by a low pressure blower during normal operations or by high pressure air during emergency situations.  Either way, its effect upon the submarine is positive buoyancy.

Answer 2

the total weight of the mass inside the submarine envelop falls, but its volume in water is rigid and stays the same, so it tends to float.