This aquatic plant is not common in Monterey County. It would not be listed here, except that can be highly invasive. The leaves are distinctive, 5–8 mm wide, oblong, thick and more or less wavy, with clear veins and rounded tips.
Long-leaved Pondweed – Potamogeton nodosus
Stems < 300 cm
Shallow water, lakes, ponds & streams
This has leaves of 2 kinds, which are slightly different. The floating leaves are 5–10 cm long, up to 5 cm wide, elliptic-lanceolate in shape, with parallel veins (typical of monocots). Flowers are in a small, decumbent to erect spike.