400 adult individuals of the Stramonita haemastoma were collected from a pristine beach in Ceara State, Brazil. These organisms were transplanted into a marina with intense shipping activities and were fed weekly with oysters obtained from the same beach from which they were collected, being exposed only to the bioavailable organotins in the environment, without accounting for diet (waterborne exposure). 30 individuals were analyzed every 2 weeks after transplantation to investigate the development of imposex. After 15 days, 90% of the females had developed imposex (VDSI I-III, RPLI 3.22), with 100% of the females developing imposex after 30 days; at the end of the experiment, the VDSI levels ranged between I-V. These results were compared with those of a previously published study performed simultaneously in which gastropods obtained in same area were fed in the laboratory with oysters from the same marina in which the gastropods were transplanted (dietborne exposure). Despite the higher levels obtained through exposure via water at the end of 90 days, both exposure routes induced imposex in 100% of the females of the S. haemastoma. However, aqueous exposure induced higher levels, possibly due to the constant contact between the organisms and contaminants.