There are a few additional wetland plants to consider in addition to giant cane, common reed, and papyrus. Like so many other references it is not possible to state with certainty the botanical names of these plants. Several candidates are likely, however, for the words translated from the Hebrew tse'el.
"Under the lotus plant (tse'el) he lies, hidden among the reeds (qaneh)," Job 40:21 and 40:22, "the lotuses conceal him in their shadow; the poplars by the stream surround him.". The King James Version translates this verse as, "under the shady (tse'el) trees ('ets). This description of the behemoth includes its riverine habitat. It is unfortunate that NIV translators used "lotus plant" in this verse. Lotus is the common name applied to water lilies, most often Nelumbo lutea. But it is also the Latin name of a genus of legumes, Lotus. Species of this genus are not aquatic plants. What is this mysterious plant linked with the likewise enigmatic behemoth?
Tse'el can mean, among other things, stalk or stick--in any case implying something slender. This could hardly be Nelumbo which has large round, usually floating leaves up to 1m across. A tall, sender, stick-like plant could be giant cane or common reed which would fit here except that qaneh is used later in the same verse. Papyrus could conceivably fit the description except that in Job 8: 11 the word achuw is translated papyrus.
Could this mysterious plant be one of the other aquatic plants frequent in the Middle East? In the context of Job 40, it should have the following features: form a stand dense enough to hide the behemoth (" . . . under the lotus plant he lies"); grow in a stream that might flood ( . . . "when the river rages"); be part of a guild that includes poplars, possibly Populus alba (v. 22); and be a plant compatible with vegetation found along the Jordan River (v. 23).
Of plants found under such conditions, the most likely is Typha domingensis known in English as cattail. It forms dense stands and has long, narrow leaves that would be within the circumscription of the Hebrew word for something slender. The thick heavy rhizomes can withstand flooding and it is a common plant in the Jordan Valley.