Cold water shock and the 1-10-1 rule

Most boating deaths in cold water happen in the first few minutes, long before hypothermia sets in. The cause is cold water shock: an involuntary gasp and rapid breathing when you hit water below about 60°F (15°C).

The 1-10-1 rule

Cold water researchers summarize the timeline this way:

• 1 minute. The gasp reflex and hyperventilation. If your head is under water when you gasp, you can inhale water. A worn life jacket keeps your face up while you get your breathing under control.
• 10 minutes. Meaningful movement. Your hands and arms lose strength fast, so use this time to climb back on, right the boat, or get to something that floats.
• 1 hour. Roughly how long before hypothermia makes you lose consciousness, depending on water temperature, body size and clothing.

Why lakes catch people out

Air temperature in spring can reach the 70s while the lake is still in the 50s. Big, deep lakes warm slowly and can stay cold well into June. Mountain reservoirs stay cold all summer below the surface.

What to do

• Wear the life jacket, do not just carry it.
• When the water is under 60°F, dress for the water, not the air: a wetsuit or drysuit for paddling.
• Stay close to shore and paddle with someone.
• Leave a float plan with a friend.

Lakeglance shows water temperature when the lake’s USGS gauge reports it, and drops the paddling call to Use caution when the water is under 60°F.