There will probably never be a real known "cause",.. but speculation is that it was a combination of dehydration from the undiagnosed diabetes (I was drinking a lot, but I was also urinating a lot) & a break from the post- decompression dive protocols I was taught. Normally after coming up from a decompression dive, we hang out on the surface & just chill out for 10- 15 min.,... discuss the dive, we then jettison all bailout/ stage & decompression cylinders at the water's edge, leaving only what we have on our backs. We then get out of the water, drop the equipment on our backs & sit down to rest for another 45- min to an hour to allow proper off gassing before removing dropped cylinders from the water & loading the vehicles to go back to our rooms. That particular day, we had completed a rather long CCR dive, done the prescribed decompression, but, instead of taking the time to rest on the surface & afterwards on land, we immediately pulled the equipment from the water & began loading my truck for the trip back to the motel we were staying in. We left Ginnie Springs at about 1 in the afternoon & by 6pm, I was showing symptoms.