my white's always had a deep water feature in their tanks.never once did any drown. i have seen herpetologists who keep whites in a tank 3/4 filled with water and floating land pieces for them to rest on. there is a lot of conjecture in this topic due to not many people willing to build tanks with water features for frogs because they read that they may drown. i did quite a bit of research before building my white's tank with a 10" deep water section and could not find one first hand account of a frog drowning. in fact every tank i built for white's, i often saw them intentionally jump in the water or spend hours soaking in it. just give them easy exit points and they will be fine. oh, and this goes for darts as well.