While I agree that darts rarely do drown, I stick with the old opinion: that darts do not like water (which they don't, imo).
Most people say that they are poor swimmers, which is not especially true, unless you are dealing with froglets. I have seen with my own eyes a dart (a vent) that was perfectly healthy, but crashed into the newly cleaned glass by the water until he no longer could keep himself above the water's surface. Attempts to save him were vain, as about 15 minutes in, he died (probably from head trama more so then drowning). And though these types of things can work well, the space can be used so much more practically! Hell, when does a dart ever get a meal from a water feature?
Also, about very few drowned fruit flies, what is your setup? When I was working with geckos a few years back close to 60% of the ff drowned. IS there a way to avoid this?
So maybe this is a stupid question, and to be honest I have never had darts, but why in the world would someone let a dart (which I understand are a pretty expensive frogs) crash into a newly cleaned glass over and and over until it couldn't keep itself above the water's surface AND then worry about trying to save it? Seems kind of silly to me, I would think that the logical thing to do would be to move it, so it quite crashing into the glass in the first place. Also, if they don't like water, why was the dart swimming in the water in the first place?
Not trying to offend, just don't see a whole lot of logic being applied in that story, so I'm curious.