Bad Things You Need To Know About Falling Into The Sea
In December we published a blog article about Man Overboard drills. This article describes some of the consequences of a Man Overboard from a medical viewpoint. Keep in mind that the day it was posted here, BrambleMet showed a water temperature of 9oC… only slightly warmer that the inside of most fridges. Ed.
Written by NCI Watchkeeper Dr Chris Aps
FRCA
UK waters are cold. Around Portsmouth the coldest sea temperatures are seen in February and March and are between 7 and 9 degrees Celsius. Although warmer in the summer, reaching a peak in September, it rarely approaches 20o C. Bearing in mind your normal core temperature is 37o C, the difference between your temperature and the sea’s is huge, whatever the time of year. The bigger that difference, the more quickly heat energy escapes from your body into the water.
People think that swimming and thrashing about will help you keep warm if you fall in. Wrong. Moving your limbs in effect makes water flow over them, which in turn increases the amount of your skin exposed to the water each second, effectively increasing your surface area extracting more heat out of you. Think wind chill, but in water. This is why the RNLI advise you to move gently and preferably curl up into a ball to reduce your surface area exposed to the cold water. Be aware that children’s bodies have a larger surface area compared with their weight than adults, and they will lose body heat even faster.
It gets worse. Physics will tell you that heat is conducted far better in water than air, which means that heat loss from your body is 20 to 25 times faster in water. That explains why people get cold so quickly when immersed. The clothes you are wearing will influence how cold you get. Summer boating in T shirts is great until you fall in.
Hypothermia is clinically defined as a body core temperature of 350C or less. One of the first signs of developing hypothermia is the inability to control movements of your fingers, hands and limbs. Don’t expect that someone who has fallen in can necessarily help themselves to get out. If it is you, then don’t be surprised if you can’t grab that rope that has been thrown for you. The brain is part of your body. When that gets cold, it doesn’t work as well. You will find it difficult to think, communicate and may fall unconscious. If that happens you are severely hypothermic.
All this assumes that you have survived the initial falling in without getting Cold Water Shock. This kills those people who get a severe body reflex reaction to sudden, perhaps unexpected cold-water immersion. The heart and circulation go into overdrive, which itself can be fatal. Worse is the uncontrollable gasp reflex that can mean you inhale large volumes of water, then drown. This is why the RNLI advise people to avoid gasping, remain as calm as possible and turn on their back and float instead.
National Coastwatch watch-keepers and all HM Coastguard’s teams take “persons in the water” situations very seriously. So should you. A person who falls in the water is a person in grave and imminent danger requiring immediate assistance. If you witness this, dial 999 and ask for the Coastguard who will task the Search and Rescue Services. If you are on a boat, make a Mayday call on distress VHF channel 16. Also, if you are boating always wear a lifejacket; it could save your life if you happen one day to be the casualty.
