We performed large-scale molecular-dynamics simulation of nanoscale hydrophobic interaction manifested by the formation of nanobubble between nanometer-sized hydrophobic clusters at constrained equilibrium. Particular attention is placed on the tendency of formation and stability of nanobubbles in between model nanoassemblies which are composed of hydrophobic clusters (or patches) embedded in a hydrophilic substrate. On the basis of physical behavior of nanobubble formation, we observed a change from short-range molecular hydrophobic interaction to midrange nanoscopic interaction when the length scale of hydrophobe approaches to about 1 nm. We investigated the behavior of nanobubble formation with several different patterns of nonpolar-site distribution on the nanoassemblies but always keeping a constant ratio of nonpolar to polar monomer sites. Dynamical properties of confined water molecules in between nanoassemblies are also calculated.