Years ago, when I was a kid, I remember seeing this cartoon that involved a guy who piloted a giant robot that turned into a truck. The kid would drive the truck over these platforms that would rise out of the water, and then the truck would be lowered (I think) to an underwater base. The kid was attached to the robot and piloted it. I don't know if this was some dream that I had, which merged a number of different cartoons with my imagination, or if it's something that I really saw. Can anyone help?