Via molecular dynamics computer simulations, we have studied the free energy of water transfer into alkyl interfaces having varying levels of unsaturation. The chain length and hydrophobic slab thickness were chosen to model lipid bilayers where polyunsaturation has been observed experimentally to affect numerous structural and permeation properties of the membrane. The polyunsaturated alkyl chains follow a pattern of two successive single bonds separating vinyl groups, mimicking the pattern found in polyunsaturated lipids. The calculated free energies of transferring a single water molecule through n-hexadecane, 8-hexadecene, 5,8,11-hexadecatriene and 2,5,8,11,14-hexadecapentaene are 7.4, 7.1, 6.7, and 6.2 kcal/mol respectively. The decreasing transfer free energy with increasing level of unsaturation is consistent with experimentally measured permeation rates.