In the preceding paper, the structure of water around a model protein alpha-helix (made from polyalanine) was investigated using two-dimensional projections of the molecular distribution function. Here an attempt is made to assess the relative importance of packing, protein-water hydrogen bonding, and water-water hydrogen bonding in creating this water structure. To isolate the effect of protein-water hydrogen bonding, simulations with the helix charges ''switched'' on and off were compared. Likewise, these ''normal'' water simulations were compared to ones done with the water charges switched off to assess the relative contributions of packing and hydrogen bonding. The energy of water molecules around the helix was also investigated. The results show that water-water hydrogen bonding, which underlies hydrophobicity, is the dominant interaction. On average it moves water molecules back from hydrophobic parts of the helix surface as compared to water molecules around hydrophilic parts. Furthermore, completely disrupting this interaction by switching off the water charges moves the solvent molecules in toward the helix, making narrow crevices more accessible to solvent. This result has important implications for the interpretation of Richards-Connelly molecular surfaces.