What are Sea Legs? And, can they help ward off seasickness? We will find out why this
is an often overlooked, yet important skill to have when diving. Here we will describe the
technique of getting your sea legs to assist with balance on dive boats and to help ward
off seasickness.
What’s with the Name?
The term sea legs is a metaphor for adjusting to living, working or traveling at sea.
Sometimes it is used to describe the imbalance one feels when coming back on land
after being exposed to the motion at sea. But here we will describe the technique of
getting your sea legs to assist with balance on dive boats and to help ward off sea
sickness.
What’s Our Body Doing?
First, what is it that makes us off-balance and/or seasick to begin with? Well, consider
that we are terrestrial beings. We live on land where gravity continuously meets with our
laws of motion. Our bodies use multiple sensory stimuli to interpret and regulate our
motion. Within our inner ear the semicircular canals are responsible for detecting motion
of the body. The fluid in the semicircular canals combined with hair cells in the inner ear
transmit motion information to the brain. The brain interprets this input along with other
sensory stimuli such as sight and touch. When there is disagreement between these
stimuli (i.e. you’re sitting or holding onto something while rocking back and forth, or
you’re staring at a non-moving object yet you are moving up and down) then you may
experience loss of balance and/or seasickness.
The Technique
One of the best ways to minimize that disagreement of sensory stimuli is to minimize
movement of the head. And how we do that on a dive boat is the basis for our sea legs
technique:
- Keep your head upright and straight. Every second of the waking day your body is
making adjustments of how to keep the head upright – whether sitting, standing,
walking, running, or riding a roller coaster. So, we are very conditioned to keep our head
level. When we keep our head upright and straight, the horizontal plane of our ears and
eyes is parallel (level) with the horizon. This prevents much movement in the
semicircular canals. In fact, recent research from the University of Minnesota shows that
the old sailors’ adage of “look at the horizon” actually has merit. The study concluded
that looking at the horizon stabilizes one’s posture. Whereas looking at an object on a
moving boat increased sway, thus increasing movement of the head. - Bend your knees and flex your legs to “ride” the wave motion. Like most sports, to
keep a good center of gravity the legs must be slightly bent. This allows the legs to
respond quickly and act like shock absorbers to keep the upper torso of the body stable
and ready. On a moving boat, we want that same stability of the upper torso mostly
because it will also keep the head from moving. Simply, bend and flex your legs with
every motion of the boat. Doing this while keeping your head up and looking forward
allows you to see the incoming waves and see the boat rise and fall. You want your legs
to flex up and down as they ride each wave – again, keeping your head upright, level
and as motionless as possible. In time, your body will sense the stimuli and make
adjustments on its own. For instance a seasoned divemaster can work the back of a
boat, not seeing the oncoming wave, but as the boat rises the signal sent through the
feet as they begin to flex with a wave goes to the brain to make other postural
adjustments to keep the body upright and balanced.
I hope you can now see why it makes sea sickness worse to go into the head of a boat
(motionless surroundings, while motion is occurring) or to lay down (head is not upright
and straight). Note that this is a technique that needs time to be learned and that there
are some who are chronically seasick whenever they go on a boat. In other words this
does not work on everyone. And note too that if someone has been vomiting
excessively, they may be too weak to stand up and keep balanced.
So next time you’re on the dive boat give this sea legs technique a try. Remember to
focus on keeping your head still and your legs flexed. And finally, no matter how good
your sea legs are, HOLD ON to solid objects for stability whenever you are on a moving
boat!
