It is true that being polar, the water is more attracted to other water molecules on the same side of the membrane than to the hydrocarbon chains that are in the bilayer. When the water molecules are 'buzzing' around, some of them just slip through. Protein pores and carriers are not involved and in fact, water will diffuse across an artificial lipid bilayer which doesn't even have proteins. It won't diffuse as quickly as if the lipid bilayer were not there, but it will diffuse rather easily. Now you mention water soluble substances, which would refer to polar and charged molecules.
Ions generally require membrane proteins to get through as do larger polar molecules.
It is called Osmosis and the Marvelous Membrane' and deals with using decalcified eggs to demo osmosis. They mass their eggs, put in solutions, and mass them again every 10 or 15 min for 1.5 hrs. It also will work in a 45 min period if the kids come back at lunch or later to mass them after class. Then plot percent change in mass vs time. The article I reference above recommends using glucose solutions, but I have found that sucrose works as well and is a whole lot cheaper.