I forget what they are called, but I have heard of places that immerse you in total darkness and total silence and have you float in water that is the same as your skins temperature so that you feel like you are floating in nothingness. I never went but want to try it sometime. So I cannot say if it works or not but at least according to these places you would not feel the water. I wish I could remember what they were called. We have one here in Atlanta.

EDIT: found it based on SCHiM's comment: http://flo2s.com/floating/what-is-a-float-tank/