During the first class, I have my students start with the hull of the ship, water line and the underwater scene on the first day. I ask them to focus on adding a lot of details. I don't review shading and value until the very end.
During the second class we focus on the deck of the ship and anything they want to put in the sky. The third class they may add pirates. My requirements are at least eight different pirates with different clothes.
The fourth and fifth classes are spent shading in their drawing. We start with a value scale and I ask them to use that to add all the different values from that value scale into their drawing. I was very pleased with them this year. Many added a lot of creativity and plenty of shading.