Geovishaps have 30% physical resistance, 50% Geo damage resistance and 10% resistance for other elements. Even if you have physical damage characters like Razor or Eula, you will deal less damage than your elemental counterparts. Sure, Geovishap, as the name sounds, is a Geo-based beast, so you can expect Geo resistance on it. But, this doesn't mean that you cannot deal Geo damage to it, you can deal Geo damage, but it'll be less potent.  If the Geovishap absorbs a particular element, its resistance to that element increases by 20%. If a Geovishap is infused with Hydro element, its resistance to that element is 30%.  Geovishap's base resistance to Hydro is 10%, and after Hydro infusion an extra 20% gets added to the resistance stat. Unless you have a hyper carry of that element, I won't recommend dealing Hydro damage to a Hydro infused Geovishap.