Fluctuating gaps, generated by thermal perturbations between a hydrophobic solid and water, because of their incompatibility, are considered to be responsible for the long-range attractive hydrophobic force. Their formation is stimulated by the traces of air dissolved in water, The pressure field induced by the fluctuations of one of the water surfaces acts upon the fluctuating gaps of the other surface generating an attractive force. Equations are obtained which predict a dependence of the force on the viscosity eta of the liquid of the form eta(-2) This dependence can explain the threefold increase of the force for a change in temperature from 20 to 40 degrees C observed experimentally. This observation brings support to the suggestion that the hydrophobic force may have a hydrodynamic origin.