Cause of Death?

Here's something to chew on:
Imagine that, for some reason, someone tied cinder blocks to your feet and threw you to the bottom of an empty pool. You look up to find that this someone has a truck full of water, and a truck full of sand. If they dump the water into the pool you would die by drowning, right? If they were to dump the sand into the pool instead, you would die by suffocation. What if they dumped half and half? Where is the threshold where if you add more sand you'd suffocate instead of drown? I've done this experiment on at least a dozen winos, and I still don't know for sure; but I can tell you that it's somewhere in the 45-55% sand range...