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New DiverWire Feature – Ask the ScubaGuru: What are “Sea Legs”?

DiverWire is pleased to announce it is working with Tec Clark of to provide answers to interesting diving-related questions. Each Friday, starting this week, we’ll have a new question and answers from “the Scuba Guru.”

Boat divingWhat are Sea Legs? And, can they help ward off seasickness? This is an often overlooked, yet important skill to have when diving. Getting your “sea legs” assists with balance on dive boats and helps ward off seasickness.

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 sacculus and utriculus 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:

1. 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.

2. 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 seasickness 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!

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