As you can see in the attribute table, the layer that you have created does not have any height information. You need water height information to extrude the layer properly in the 3D scene. Therefore, you will add a new attribute to the table and give it desired values.
At the top of the attribute table, click the Field Add button. The Fields view opens, where you will be able to edit parameters.
For the empty field at the bottom of the table, under Field Name, type Height. For Data Type, choose Float. Choosing Float over Integer allows you to have decimals.
On the ribbon, on the Fields tab, click Save. The changes will be added to the table.
Close the Fields view. Return to the attribute table.
On top of the attribute table click the Calculate field button.
The input table is Flood_Zone_Campus. The field Name is Height. For the expression, you will consider 5 feet of flood for areas around the floodways. This number is for presentation purposes and is not accurate. Click OK.