If you're hung over on the morning of departure from the previous evening's social events, chance are good that you will donate your breakfast to Neptune. Feel free to eat moderate amount of whatever foods you find appealing. Diet becomes important only if vomiting occurs. Sometime a case of seasickness is limited to a single episode of vomiting. Vomiting brings temporary relief from nausea, but after several episodes, weaknesses, drowsiness and apathy typically result.
Sufferers usually are able to respond physically to real emergencies for a day or so.
Your breath will smell like acetone. It won't all stay down, but your net loss of fluid, glucose and electrolyte due to vomiting will be much reduced. Watch leaders should be alert for weaknesses, extreme drowsiness and confusion in those suffering from prolonged seasickness. Severely afflicted crewmembers are often reluctant to go below because they might feel worse and they don't want to leave the rest of their watch shorthanded. Instead, they linger on deck, sometimes even falling asleep at the leeward rail.