Objectives: The role of the cardiovascular system in the development of seasickness remains uncertain. Material and Methods: Overall, 18 healthy students (10 males and 8 females) aged 18–24 years volunteered in the project, spending 2–7 h on life rafts. The cardiovascular system was examined with impedance cardiography. Susceptibility and symptoms of seasickness were evaluated by the Motion Sickness Susceptibility Questionnaire Shortform (MSSQ-Short) and the Motion Sickness Assessment Questionnaire (MSAQ). The Visual Analogue Scale (VAS), ranging 0–10, was used to assess nausea, dizziness and mood. The parameters were assessed at 2 time points. Results: Differences in the heart rate (HR), the thoracic fluid content index (TFCI), the stroke index (SI) and the Heather index (HI) before launching the life rafts and after leaving them were observed (78.6, 20.8, 55.6 and 15.9 vs. 70.1, 19.7, 60.5 and 17.9, with p-values of 0.002, <0.001, 0.003 and 0.004, respectively). Females reacted with changes in SI and HR more vividly, whereas males regulated more HI and TFCI. In addition, HR correlated significantly with the central and peripheral symptoms in MSAQ, stroke volume (SV) with peripheral and sopite-related ones, SI with overall ones, and pulse pressure with overall, gastrointestinal and central ones (Spearman’s rank correlation coefficient [ρ] was –0.478, –0.711, 0.476, 0.472, 0.525, –0.476, –0.579 and –0.584, respectively). As regards MSSQ-Short, it correlated negatively with sopite-related symptoms in MSAQ (ρ= –0.486). Mood in VAS correlated significantly with gastrointestinal symptoms, SI and the cardiac index (CI) (ρ = –0.752, –0.492 and –0.489, respectively). Conclusions: It was found that HR correlated negatively, and SV/SI correlated positively, with the severity of seasickness symptoms measured with MSAQ. Gender is probably an independent factor influencing reactions to motion. Women react with SI increase whereas men react with increased heart contractility (HI rise). Negative mood in seasickness evaluated with VAS seems to be mostly determined by gastrointestinal symptoms assessed with MSAQ and diminished cardiovascular indices (both CI and SI). Int J Occup Med Environ Health. 2020;33(4):467–77