How to draw Flexitank in SolidWorks and animate it in SolidWorks Composer?

Hi, I'm working on designing a shipping container with flexitank.

I wonder how to draw a flexitank in SolidWorks and animate it in SolidWorks Composer.

I wish I can create an animation to show to my customer.

Here is the example:

http://www.liquatrans.com/video2.php?id=31

SolidworksComposer