Ambulia sessiliflora, emersed
True Aquatic plant, requires medium light
There isn't a much easier to grow plant. This stock is grown out (for quick, inexpensive supply) under root wet/plant "dry" conditions and is therefore supplied in it's hardened, emersed form.
Under aquatic conditions it soon softens into it's submersed growth. For more immediately lush growth see Limnophila sessiflora, submersed.