The gravitational pull is the key. Saturn would either incorporate the water into its own mass, or be dissipated by it due to the gravitational forces created by such a huge water mass. Not to mention that you would need an immensely large amount of water (way larger than the Sun) for it to have a "flat" surface (this is, the curvature radius of the water body would need to be immense in comparison to Saturn) in which to put Saturn to see if it floats. So, no. It would not float, regardless of its density.
I have always been against this kind of stupid scientific simplifications, because they involve disregarding facts to an extent in which the point that is being illustrated is either absurd, or no longer valid/relevant. Science doesn't need to be "funny".
[EDIT]
Hey, come think of it, that was pretty useless! :D
Beat that!