The ovate leaves at the surface look a bit like the very common P. natans (Broad-leaved Pondweed) to me anyway. However the submerge leaves are a different shape being longer and narrower more like P polygonifolius (which doesn't help if you don't know what that looks like). The problem with these pondweeds and many water plants is that you often can't get very close or have to set up a camera with a good zoom lens on a tripod to get a decent photo. These plants were past their best anyway but are a native rarity nonetheless.