I am the music director at my church and this year, I'm directing a mini-musical for the kids which is all about exploring God's underwater world. I've got a good handle on all the underwater scenery & stuff - the kids are gonna dress up as various sea creatures, & i'm painting/cutting seaweed & coral stuff out of cardboard. My problem is that the 5 main characters are to be in a submarine. I cannot figure out how to make a submarine to fit at least 5 kids! First let me tell you that I have basically no budget & very little help. I usually am involved in the musical aspect of my community theatre, so I don't know much of the set design terminology or processes, but I am a very good artist & love designing things. So for the submarine, we don't neeed to see the whole entire thing, just someway to make it look like the kids are in a submarine from the front view. First I was thinking of going the cardboard box route, but i would rather it have a rounded look, like a real submarine, not a boxy look. What are my options as far as different materials I could use? Any ideas on how to create this fairly cheaply would be GREATLY appreciated! Thanks!

Does the submarine have to move?  If not just designate a part of the stage as the submarine.  it could be a grouping of chairs, perhaps a periscope and or a steering wheel.  have the kids mime getting in and out.