Herbs, annual or perennial, submerged or floating, aquatic, in fresh or brackish water or marine. Stems short or elongated, sometimes stoloniferous. Leaves radical or cauline, alternate, opposite, subopposite, whorled, or pseudowhorled, sessile or petiolate, usually sheathing at base. Flowers unisexual or bisexual, actinomorphic, enclosed in a bifid spathe or within 2 opposite spathal bracts, or rarely not spatulate; spathes sessile or pedunculate. Stamens 1 to many, occasionally some staminodal; anthers 1-4-thecous. Ovary inferior, 1-loculed; carpels 2-15, fused; ovules few to many, on parietal, sometimes intruding placentae; styles 2-5; stigmas usually bifid. Fruit a fleshy and berrylike capsule dehiscent or opening by decay of pericarp, or an achene (Najas). Seeds numerous, usually small, without endosperm; embryo straight.

Wang Huiqin & Sun Xiangzhong. 1992. Hydrocharitaceae. In: Sun Xiangzhong, ed., Fl. Reipubl. Popularis Sin. 8: 151-190; Zhou Lingyun, You Jun & Zhong Xiongwen. 1992. Najas. In: Sun Xiangzhong, ed., Fl. Reipubl. Popularis Sin. 8: 108-125.

Eighteen genera and ca. 120 species: widely distributed in tropical and subtropical regions of the world; 11 genera (one introduced) and 34 species (four endemic, one introduced) in China.

(Authors: Wang Qingfeng (王青锋)[19], Guo Youhao (郭友好)[20]; Robert R. Haynes[21], C. Barre Hellquist[22])