This CIA toolkit is built for concealing in a spy's butt

Not the point.
The tape’s function is to prevent the container from opening. Because there are sharp and pointy things in it.
But both the container and its contents are waterproof/waterresistant.

If if you’d want to use to container to carry anything beside the toolkit, there is always the option of waterproofing those items separately, like, for example, putting them in a condom.

Come to think about it, stuffing something else in the container to prevent the toolkit from making unwanted clinking sounds would probably a good idea.