Seasickness — the first 72 hours protocol

Seasickness typically resolves within 48-72 hours as the vestibular system acclimatises. What to do — and when it becomes an emergency.

Seasickness (motion sickness) affects most cadets + returning seafarers during the first 24-72 hours of a rough passage. It is caused by sensory conflict between the visual + vestibular systems. Vast majority resolves within 72 hours as the vestibular system acclimatises. Severe cases can cause dangerous dehydration — the classic pattern is progressive vomiting + fluid loss + electrolyte imbalance leading to reduced ability to keep down oral fluids or medication.

Practical steps

• Fix your gaze on the horizon — never on close-in reading or screens.
• Fresh air on deck; avoid the galley + engine-room during acclimatisation.
• Anti-emetic (cyclizine 50 mg or ondansetron 4 mg) at first onset — much more effective before severe nausea.
• Sip clear fluids (water + electrolyte solution) every 15 minutes even when nauseous.
• Ginger tablets (250 mg) have modest evidence + no side effects.

When to escalate

• Unable to keep fluids down for 24 hours — dehydration risk; TMAS consultation for possible IV fluid.
• Persistent seasickness beyond 96 hours — rare but suggests underlying vestibular problem; shore-side ENT consultation.
• Any sign of electrolyte imbalance (muscle cramps, confusion, cardiac irregularity) — medical emergency.

Last verified 3 months ago