Dictionary.com's Word of the Year is...
A plant that grows wholly or partly submerged in water. Because they have less need to conserve water, hydrophytes often have a reduced cuticle and fewer stomata than other plants. Floating leaves have stomata only on their upper surfaces, and underwater leaves generally have no stomata at all. Because water is readily available, hydrophytes also have a reduced root system and less vascular tissue than other plants (which also makes plant parts less dense and helps them float). Hydrophytes tend to have less supportive tissue as well, since they are buoyed by water. Many species of hydrophytes (such as the Eurasian milfoil) have divided leaves that have less resistance to flowing water. The lotus, water lily, and cattail are hydrophytes. Compare mesophyte, xerophyte.