Metamucil recommends 8 ounces of water be taken due to the possibility of choking, but there are conflicting reports on whether this is necessary. Psyllium husk powder does soak up water quickly (quicker than mortar does) and if taken dry there is a chance you will choke to death, but you would probably have to drink it pretty dry to have that happen. I would not recommend trying it to see what happens. If you have trouble swallowing or a narrow esophagus, be careful.
My CCFA support group leader/moderator is aggressively opposed to taking metamucil with a lot of water. Not really sure why, or where the harm is.