Any type of unusual motion can cause seasickness, such as wave action in bad weather or high wind conditions.

Each person’s pattern of symptom onset is somewhat different, but it is usually repeatable. Generally the first symptoms are yawning and drowsiness, then abnormal fatigue and lethargy, but if you already are tired from standing watch these symptoms can go unrecognized. For many people, the first obvious symptoms can go unrecognized. For many people, stomach awareness and slight cold sweating are the first noticeable symptoms.

As symptoms advance, stomach awareness turns to nausea, the face becomes pale, particularly around the nose and mouth, and hands and face become cold and clammy.  Belching, salivating and flatulence are common. Concentration on mental tasks becomes difficult.  Eventually nausea comes in waves, and increases in uncontrolled crescendo leading almost inevitably to vomiting.  Subsequent attacks of vomiting typically develop with less warning than the first.

Seasickness usually quiets down as soon as the motion stops. The more you travel, the more easily you will adjust to being in motion.

• if practical, stop or minimize motion by slowing down, anchoring, or docking.
• sometimes a small course change can change the amplitude and frequency of the boat’s motion in the waves, often with miraculous results.
• if you sense the onset of seasickness (light-headedness, nausea), move out of enclosed cabin areas to the middle of the ship, or the cockpit.
• take an anti-motion sickness medication, if you have not done so already.
• focus on the horizon or on a distant, stationary object.
• keep your head still, while resting against a seat back.
• if you have experience as a helmsman, take the wheel and steer by reference to oncoming waves, the horizon, clouds and distant sails.
• do not read.
• do not smoke or sit near smokers.
• eat dry crackers or drink a carbonated beverage to help settle your stomach if you become ill.
• replace nutrients after repeated vomiting.  If you don't eat and drink because you feel nauseous, eventually you will become weak, confused and eventually incapacitated.  Your breath will smell like acetone.  To prevent this, force yourself to eat and drink (broth, saltines and candy, for instance) frequently in small amounts.  It won’t all stay down, but your net loss of fluid, glucose and electrolyte due to vomiting will be much reduced.

The key to effective prevention is to recognize and react to your earliest symptoms.

• avoid spicy and greasy foods and alcohol.
• do not overeat.
• take an over-the-counter seasickness medication, such as Gravol or Dramamine. at least 30 to 60 minutes before you travel.  Expect drowsiness as a side effect.
• consider a scopolamine transdermal patch, available by prescription.  Take several hours before you plan to travel. Apply the patch behind your ear for 72-hour protection.  Scopolamine can cause pupil dillation for many hours, so be careful not to transfer the medication to your eyes.  Consult your doctor before using the medication if you have health problems such as asthma, glaucoma or urine retention.