If you find this symptom, then check this step:
time did not know how to + THEN Where time is initialized:
Create the OceanQueue class and its methods
add: THEN Where occupants is set to a new OrderedCollection:
Create the Ocean class and its methods
Ocean does not know if something is food THEN Where the reference to ocean is made:
Create the mainline (System Workspace) code that will run the system
Hints: Check the code carefully. Use inspectors on anything that the system says does not understand something -- the inspector will tell you what class something is.