I'm not an expert by any means, if it were I, I would recommend first, Texas A&M , plant.tamu.edu/plant-identification . Texas A&M website for water plants. excellent resource, if you get a handful and crush it and it stinks , skunk or garlic smell, then most likely (sp) Chara (sp) , an algae , my pond is infested for first time this year. If you can't figure out from TAMU Website, get a good sample , spread out on white paper , plus maybe a second sample in clear water, in clear clean jar so the experts can see it spread out and in jar, looking as natural as possible. Dozens of water plants look like your photo, plus the glare, cloud reflections, etc corrupt your photo's . Good Luck with it, Welcome to Pond Boss Forum and Highly recommend that you subscribe to Pond Boss magazine , to assist with your water management responsibilities . Hope I've helped.

I Subscribe !