Various morphological and physiological features ofSypharochiton pelliserpentis(Quoy & Gaimard, 1835) were examined in relation to the different physico‐chemical characteristics experienced at 4 sites on Kaikoura Peninsula and 2 sites in the Avon‐Heathcote Estuary. Body water content of chitons from high‐shore exposed and estuarine rocky sites was significantly greater (P<0.005) and desiccation rates were significantly less (P<0.05) than those of chitons from low‐shore marine sites and an estuarine mudflat. The percentage of body water loss causing death was greatest for high‐shore marine chitons and least for estuarine chitons. Estuarine chitons had relatively more gill tissue than marine individuals. Body shape appeared to be correlated with intensity of wave action, and narrow animals were found in more wave‐exposed areas. Variations in radula length showed no clear‐cut trends among localities.