Yeah, Hymenochirus sp are fully aquatic, as are all Pipid's, they will usually try to find a way to escape aquariums though, so not sure if they sometimes leave the water in the wild if the conditions are humid enough? ive also been told that Silurana (Tropical and Cameroon Clawed Frogs) species like to sometimes bask above the waterline apparantly, my ones sometimes sit on the plants slightly above the water line, they dont have access out of the water other than that though.
I've heard all to often they go exploring, or are found sitting on floating tank decor for awhile and will come out to eat. They may be aquatic but they do come out to stretch their legs now and then.