1) An aquatic plant 2) Aquatic plant 3) Hydrophytic plant 4) Tracheophyte 5) Vascular plant 6) Water plant 1) Awlwort 2) Bogbean 3) Buckbean 4) Cryptocoryne 5) Duckweed 6) Eelgrass 7) Featherfoil 8) Frogbit 9) Hornwort 10) Hydrilla 11) Naiad 12) Pickerelweed 13) Pipewort 14) Pistia 15) Pondweed 16) Wampee 17) Waterweed 
• (n.) An aquatic plant; an alga.
<botany> A plant which can grow only in very wet soil, or which grows with its leaves partly or completely underwater. ... (09 Oct 1997) ... 
a plant growing in water or on a substrate that at least periodically is deficient in oxygen due to excessive water content.
Plant that grows wholly or partly immersed in water; compare with xerophyte and mesophyte.
Hy'dro·phyte noun [ Greek ... + ... plant: confer French hydrophyte .] An aquatic plant; an alga. 
hydrophyte 1. A plant that grows in water or in saturated soil. 2. A plant requiring large amounts of water for growth; also, hygrophyte. 3. A plant that grows partly or completely underwater.
Plant adapted to live in water, or in waterlogged soil. Hydrophytes may have leaves with a very reduced or absent cuticle and no stomata (since there is no need to conserve water), a reduced root and water-conducting system, and less supporting tissue since water buoys plants up. There are often numerous spaces between the cells in their stems ...
a plant that grows in water or very moist ground; an aquatic plant.