Because watercress is an aquatic vegetable grown in water for a long time immersed in water, rarely absorbing light, so its flavor is much lighter than celery, and you can't eat celery at all with its aromatic flavor.

Watercress is the umbelliferae, watercress perennial herbaceous plants, stems erect or base creeping. Basal leaves are stalked, with leaf sheaths at the base; leaf blade triangular in outline. Compound umbels terminal; involucres absent; rays unequal, erect and spreading; calyx teeth linear-lanceolate, petals white, obovate, with a long and inflexed ligule; stylopodium conic, erect or branched on both sides. Fruit subquadrangular-ellipsoid or cylindrical-oblong, lateral ribs more elevated than dorsal and middle ribs, corky. Flowering June-July, fruiting August-September.