The first job is to make a hatch in the side of the cow so we can install the tank and pumps. But we don't know how the cow is constructed. What if she's not hollow? What if there's a metal frame in the way?

Cue lots of tapping the outside and trying to guess from the echo what we'll find. In the end there's nothing for it but to make the incision...

Phew, she's hollow! Thank goodness for that! And there's room for the tank.

Now it's time to attach the nozzles where the water will come out. First drill the holes

...then fit the nozzles...

...making sure to take proper precautions to avoid getting sliced hands from the rough fibreglass edges inside the cow

before sealing her back up again