duckweed: any small or minute aquatic plant of the family Lemnaceae that float on or near the surface of shallow ponds
aquatic plant: a plant that grows partly or wholly in water whether rooted in the mud, as a lotus, or floating without anchorage, as the water hyacinth
british west indies: the islands in the West Indies that were formerly under British control, including the Bahamas, Saint Lucia, Antigua, Grenada, Jamaica, Barbados, and Trinidad