Plants which grow in streams, lakes, and ponds, in drains and ditches, and in the sea are often referred to as water plants. If the term is used to include plants which spend most of their life partly submerged in water, as well as the algae which live, more or less, completely submerged, there is difficulty in defining the limits of what should be included, but there are a few ferns and some flowering plants which are worthy of note for their watery habitat. Some representatives of these will be included.