Perhaps it might be useful to indicate which "Off-Topic" forum this came from. I am uncertain what the context of this exchange was since I don't readily "see" what the preceding posts were on whatever thread this came from. I don't know what stream this was split from - the mod note does not say which one, and a look at the off-topic sub-forum does not readily suggest which one this is. But -- has the poster ( @JohnT) looked at the various "meal" threads where lotus root soups, for example, have been reported on repeatedly?
There have been many posts about lotus root soup on the dinner/lunch/etc threads, for example. But perhaps the member from SA did not notice them over the years?
Nevertheless, I might also mention kangkong. One of the MOST COMMON vegetables eaten by E/SE Asian folks (=millions of people). A lot of commercial production of this no longer involves actual water (very damp soil suffices instead) but the traditional growing places were in flowing water. There have also been many posts here illustrating dishes with this "water vegetable".
Regarding "standard" watercress – there is an old Chinese story (apocryphal, no doubt; related to me by my father) about a weak, starving man finding himself on the banks of a river and in desperation pulling and eating the plants growing in the water/soggy banks --- and wondrously becoming better. It was watercress, of course; and this was the story related to me when I was growing up.
