User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-3335245-20110713154618/@comment-1011548-20110713203715

Even if it had porous skin water wouldn't leave its body by osmosis unless Gobul left the river - in fact, water would be more likely to seep into its body to equalize the concentration gradient. It's a tricky one, but I think that somehow, one way or another, it finds a way of very quickly expelling all that extra water out of its body via some means.

Actually, it'd make sense for Gobul to have gills - for something that spends ages pretending to be a piece of riverbed, it can't be very convenient to have to keep popping up to the surface for a gulp of air. I suppose it can blame its reptilian ancestry - none of the aquatic Leviathans it's most closely related to have gills (Lagiacrus, Ludroth).