Without a close up. Best guess for me is water primrose.
You are correct.
Water primrose makes fishing hard from the bank, but it's great cover for fry and fingerlings. It is easily treated with a glyphosate and a non-ionic surfactant , and it can take a week or more to completely die back. My experience is that there may still be some pop ups after the initial treatment.
Also, I would rake the dead primrose out of the water once it's dead. If not, it decays and can create algae problems.