Water Absorption in Juvederm

Once the Juvederm is injected, it draws water molecules from the surrounding area for the first day or two.  This is why some report that they see a bigger difference a few days after the injections.  This is not from the water that you splash on your face, but from the inernal tissues.  It generally does not make people really swell in those areas, but just augments the result a little bit in the first few days.  I hope this helps.

Our dermis, under the epidermis, contains collagen and water, as well as other structures and products. 
The ground substance is a fluid-like material that buffers the tissue between the collagen fibers.  It is a mucopolysaccharide hyaluronic acid.  Juvederm and Restylane are hyaluronic acids. When the fillers are injected, the molecules bind neighboring water molecules, that are preexisting,

Juvederm is hyaluronic acid, a remarkable natural product that holds water.  It is a bit like a sponge.  The water comes from the normal water in your tissues and is responsible Juvederm holding its shape for so long.  Think of it as jello, soft and pliable.  Good stuff!

Juvederm breask down by a process that absorbs water from the local tissues. This probably adds to the longevity of the product.

Yes it absorbs tissue fluids, primarily water, from the cells in the areas injected. You either mis understood the doctor or he did not make it clear enough for you the understand the physiologic action of HA fillers.