A Math function that draws water droplet shape? I just need a quick reference. What is the function for this kind of shape?

Thanks.

You may also try Maple to find a kind of water droplet as follows:
  [> with(plots):
  [> implicitplot3d(x^2+y^2+z^4 = z^2, x = -1 .. 1, y = -1 .. 1, z = -1 .. 0, numpoints = 50000, lightmodel = light2, color = blue, axes = boxed);


