Personally, i would worry less about drowning and more about difficulty keeping the water clean. Cresteds LOVE pooping and peeing in their water bowls- as in, I usually have to change and clean them every other day or so with most of my cresties.
I started off wanting to try this as well... but after having kept a crestie for a few months, realized that it really would be work to keep it clean and I'd worry about bacteria and parasites (especially entamoeba, which Cresties seem particularly prone to...)