There are two main symbols that really stick out to me. The first is the Red Convertible, and the other is the water at the very end of the story.
I think that the convertible symbolizes the relationship between Marty and Stephan. When they first buy it, it is brand new, and so is their relationship. They are on very good terms, and they are two very happy brothers. However, when they return from going to the many places that they do, Stephan goes to the army, putting their relationship on hold. The car is also put away while Stephan is gone. Marty takes care of the car very well, and keeps it in very good condition. Marty also thinks of Stephan a lot