Steelix is actually much worse than groudon, it is supposedly 9.2m long and has a mass of 400kg. If we assume that is is a cylinder of diameter 1.5m then its volume would be .75^2*pi*9.2=16.26m^3 thus it has a density of 24.6kg/m^3=.0246g/cm^3 less than 1/40 of the density of water and less than the density of styrofoam.