Hydrophobic interactions are essentially entropic interactions basically due to order/disorder phenomena in an aqueous medium.  The free energy associated with minimizing interfacial areas is responsible for minimizing the surface area of water droplets and air bubbles in water.  This same principle is the reason that hydrophobic amino acid side chains are oriented away from water, minimizing their interaction with water.  The hydrophilic groups on the outside of the molecule result in protein water solubility.  Characterizing this phenomenon can be done by treating these hydrophobic relationships with interfacial free energy concepts.  Accordingly, one can think of the driving force of these interactions as the minimization of total interfacial free energy, i.e. minimization of surface area.