Note stout, cordate leaf shape rather than spade-like characteristic of the more common H. limosa
Not sure about this ID. The juvenile sprouts look very similar to Murdannia keisak which can also be seen in photos. Also growing nearby are Alternanthera philoxeroides, Cardamine pensylvanica, Persicaria glabra or hydropiperoides (and/or Polygonum verticillatum), Ludwigia repens and peploides, among many other aquatic macrophytes.
Seen with submerged and strikingly different emergent foliation. Also not to be confused with Murdannia keisak (same color, but blades do not twist and grow only in single plane) which was growing adjacent.
Note pointed, spade-like leaves, not reniform in shape