The 'water' is piping gel colored blue. (I added a small layer of
white icing underneath the blue gel to make the water look lighter in
color.) And the cat food is cereal. Each cat chose his favorite
cat-food-looking cereal to go on his cake.
I made each a two-layer 9x13 cake, filled in between the layers, and to get the 'indentation' for the sides of the bowls, I used a tip #12 to add a thick layer. I added three layers, then tried to get them as smooth as possible (easier said than done).
In the end, they weren't perfect, but they won over the cats, and their friends.