Not a Wally sub but you want to upgrade or get a smaller one, then this is the one to get https://shop.graupner.de/webuerp/ser...11&language=en

Comes with a diving cell (small piston tank) for static diving.

Video here http://www.youtube.com/watch?v=dKKwPnIqYRk

Don't confuse it with the similar ones on eBay which use a 3rd motor to dive.