The medium that the light travels before it reaches the slits does not affect the result, assuming that the slits are narrow. Only the wavelength of the light matters.
The medium after the slits affects the spacing of the fringes, but qualitatively there is no difference with different media.
There would be no difference qualitatively. The pattern is due to path difference after the slit, which would change by a factor of refractive index $n$ and therefore would change the fringe width compared the case of air..
However, if the upper half is filled with water and bottom half is air, the pattern will change. A little analysis will tell the details of that too.