Perhaps a better example of an entirely or mostly aquatic newt would be something like
Pachytriton brevipes or
P. labiatus. I was surprised to find that
Cynops cyanurus yunnanensis overwinter on land in the wild (or at least some juveniles do). Perhaps they're not as aquatic as keeping them in captivity would lead one to believe. Same goes for
C. ensicauda, which spend much of their lives on land in the wild though they can be kept almost entirely aquatic in captivity.
I probably know less about anurans than most people here, but aren't "toads" more bulky, warty and generally found on land rather than in the trees or in the water (outside the breeding season, at least)? That seems to me distinctive enough to separate them in the mind, even though there's a grey zone in which there are some toad-like "frogs" as well as froggy toads. It all comes down to common perception and language use. When I see
Bufo, I think "toad" not "frog"
I'm now starting to wonder whether
Pachytriton have those distinct costal groves or not....