Yes it is a water soluble thread and you use it on top and bobbin. I got mine from Shoppers Rule but unless you live near St. Louis, Missouri, internet orders for you. I believe it is a Superior thread product so it might be at Joann's or Hancock Fabrics also.
They make a couple different versions of it. You will want the "Extra" version for machine sewing. There is a cheaper/weaker version for hand basting.