Westpac Marine Services, Inc.


Hypothermia Chart
32.5 Under 15 Minutes Under 15 - 45 Minutes
32.5 - 40.0 15 - 30 Minutes 30 - 90 Minutes
40.0 - 50.0 30 - 60 Minutes 1 - 3 Hours
50.0 - 60.0 1 -2 Hours 1 - 6 Hours
60.0 - 70.0 2 - 7 Hours 2 - 40 Hours
70.0 - 80.0 3 - 12 Hours 3 Hours - Indefinitely
OVER 80.0 Indefinitely Indefinitely

The use of an Immersion Suit or other buoyant thermal protective device will greatly enhance survival time.
Chart is for general reference only.

How cold is my water?

Hypothermia Facts

  • Body thermal conductivity in water is 26 times faster than when exposed to air. If you have a life raft, board as soon as possible.
  • 50 degree water equals 15 minutes before incapacity and/or unconsciousness with life jacket on.
  • 50 degree water equals 9 minutes before incapacity and/or unconsciousness without a life jacket.

Chart and facts courtesy of Winslow Life Raft Company

How cold is my water?

How to Combat Hypothermia

Keeping your body out of the water is the most effective means. Life rafts are everyone's first choice since they keep you out of the water, provide shelter along with equipment. If you are not going offshore immersion suits (which used to be called survival suits) are your next best choice. While they do not get your body out of the water, immersion suits provide excellent thermal insulation.

If dedicated life saving equipment is not in your budget figure out ahead of time what you are going to do. A dinghy is an alternative providing it can be quickly launched. If you always travel with another vessel good communications can get help there quicker. At times even items like plastic coolers become the only survival aid available although in cold waters they would not be much help.

Recovering a Victim Suffering from Hypothermia

Do not expect ANY help from a victim suffering from hypothermia. You need to have a plan to get the victim back on board without them having to climb a ladder or haul themselves on to a swim platform. You also do not want to turn a rescuer into an additional victim. Devices like a Jason's Cradle are designed specifically to rescue a victim without their help whilst (after all they are made in the UK) not putting the crew into harms way. Using a rescue swimmer will work providing they are trained and have proper equipment such as an insulated dry suit. Just wearing a life jacket isn't enough if the water is cool enough to make the first victim hypothermic.

revised 10/2019