Is there some trick to vacuum sealing broccoli?
I'm sorry that you're having problems with my book. I think the problem is that you're adding water to the pouch. In the recipe, step 4 asks you to: 


  Vacuum-seal the broccoli, butter, and a pinch of salt and pepper in a
  large pouch so that the florets are in a single layer.


This will crush the tops a bit, but it will be much easier to seal. Sorry again.