A good source of information on Shallow Water Blackout is the book BlueWater Hunting and Freediving written by Terry Maas. Because Shallow Water Blackout has claimed so many top freedivers, Terry has posted his entire chapter on Shallow Water Blackout on his Web site.

On a rare occasion, an article will appear in a local newspaper describing the discovery of an abalone diver who died without explanation. Found floating but without any indication of drowning, a subsequent autopsy reveals no heart problems or other cause of death. For all intents and purposes, the individual fell over dead. This "Sudden Diver Death Syndrome" is not very well known either within the medical community or the public in general. The victims are typically in their mid-30s or older and are struck down in the spring following a winter of relative inactivity. It's thought that death results from cold water immersion causing heart arrhythmia.

The waters off northern California range in temperature from the mid-40s (45 F/7 C) to the high-50s (59 F/15 C). By any human measure, that's cold water. Immersed in this water without any thermal protection dooms a typical victim within a few minutes, at most.