Fill the balloon with water . This image illustrates why you don't completely fill the balloon you should always leave some room in the neck of the balloon, then as the form dries the pressure has somewhere to go and your clay wont split.
Fill nylon stocking with concrete for the base. Create gills underneath the cap with thin sheets of metal. Sculpt a mold for the cap, and press it into WET sand lined with a thin sheet of plastic, and slowly fill with concrete. Add realism by removing sma