Submarine Jeeps

This is a collaboration with my son, Arthur (age 4). He told me a couple weekends ago that he wanted to build a submarine jeep. He thinks we should do this ourselves so we can drive up steep walls through forests and explore underwater. I don't have experience building vehicles from scratch, so I told him our first step is going to be to design it. He has been working on his sketches separately. His design constraint that it has to be blue, so I made sure one of them was.