The wild Brassica oleracea, ancestor to all those cultivars is perfectly well known, and though it is found as far North as Southern England, it doesn’t grow in shallow water off the coast, it’s native to Southern and Western Europe and largely found on cliffs, especially coastal cliffs around the Mediterranean. It’s one of the more heavily studied species on a genetic level, as it’s so variable and produced so many useful crops.
Regarding the OP, without a better definition of ‘modified’ this question isn’t really answerable.
Maize looks very different from its wild relatives, especially the seeds themselves, but is appearance what you mean or genetic difference? The plant known as teosinte was only identified as the wild ancestor of maize because it’s genetically so similar, for all its different looks, whereas many cultivated citrus fruit are complex hybrids of multiple wild species, and are far more genetically distinct from their wild ancestors than teosinte is from maize, though they may appear similar aside from a change in flavour.