In the present paper, the nanocomposite laminate structure of scales from the Amazonian fish Arapaima Gigas is investigated. The structure and composition of the scales were assessed by means of X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR). The theory of Fickian diffusion is used and discussed in order to rationalize the water absorption and desorption behavior of the scales. Morphology studies and fracture analysis of the native scales were carried out using Transmission Electron Microscopy (TEM), Light Optical Microscopy (LOM) and Scanning Electron Microscopy (SEM). A fibrous layer of collagen and a plywood-like structure were observed. In order to study the mineral phase, the native scales were burned at 600 °C until all the organic components were degraded. The remaining ashes were then observed under the microscope and weighed to determine ratio of organic and inorganic components. The mechanical behavior of dry and wet scales was assessed by tensile tests and the effect of water in mechanical properties is also discussed. © 2008 Elsevier B.V. All rights reserved.