An elephant tusk fragment, excavated from the wreck site of a seventeenth-century Dutch trading vessel, has been analysed to determine the impact of prolonged immersion in a marine environment on this object. Samples taken from different parts of the fragment were analysed using inductively coupled plasma atomic emission spectrometry, automated powder X-ray diffraction, Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. These analyses demonstrated that most of the collagen has been lost from the ivory and that there has also been significant alteration of the inorganic matrix. Interestingly, it appears that there is greater retention of collagen in the outer parts of the tusk fragment than in the core. Conversely, the inorganic material is better preserved in the core. Changes in chemical composition and in the relative proportions of components were determined. In addition to providing information about the nature and extent of deterioration of ivory in a marine environment, the work undertaken has allowed an appreciation to be gained of the relative merits of these analytical techniques when applied to waterlogged archaeological ivory.