subjects with severe seasickness, who failed to habituate to sea conditions after at least six month of active sailing, were enrolled to the single-blind randomized control study. The intervention group was treated with rotatory chair stimulation at sinusoidal harmonic acceleration protocol coupled with galvanic vestibular stimulation to the mastoid processes. This unique procedure was hypothesized to promote habituation to seasickness. The control group underwent a sham procedure. All study participants filled out seasickness questionnaires at set time points following the intervention and underwent repeated step testing to determine their vestibular time constant. The number of anti-motion sickness clinic visits and scopolamine prescriptions was also recorded in the three months period following the intervention.

Inclusion Criteria:

• maximum score of 7 on the Wiker seasickness questionnaire in moderate sea conditions, with wave height of 0 - 1.5 m
• All had been sailing regularly for at least six months before enrolling in the study

Exclusion Criteria:

• history of hearing loss
• otoscopic findings of ear pathology
• an implanted electrode
• a finding of vestibulopathy on otoneurologic examination
• withdrawal by any subject of his informed consent.