Why the surface of water draining from bathtub is vortex-shaped?

Question

The surface of water in rotating basket is supposed to
be parabolic, is not it?

Answer 1

The entire mass of water has some non-zero rotation with respect to the drain. As the water is drawn toward the drain the rotational inertia(which has to remain constant) increases the angular velocity because the radius is decreasing. Much like a spinning ice-skater spins faster as she brings her arms inward toward her body.

Answer 2

it is from the rotation of the earth, water draining in the southern hemisphere goes the opposite way