I have built two. One "motorized" , one for static display.
If you build it with the motor, you will have to "sacrifice" some of the detail of the real thing. But it go's through the water like a "Bat out of Heck " ! Do yourself a favor, get a battery holder. The kit supplyed rubber band's will NOT hold the battery's in place, and when you try to use it , the battery's "Shift" and change the center of gravity. ( She will roll over on her side and "FLY" through the water sideway's ! )
If you build it without the motor, it build's into a very good representation of U - 123.
( The so called "Decal's" that come with the kit are meant to be used for the working model. If you are going to build the "Non - motorized" version, get yourself some better decal's. )