Qenya
ailin
noun. pool, lake
linya
noun. pool
linde
noun. pool
nende
noun. pool
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A noun in The Etymologies of the 1930s glossed “pool” derived from the root ᴹ√LIN of the same meaning (Ety/LIN¹).
Conceptual Development: A similar word ᴹQ. linde “pool” appears in the Declension of Nouns from the early 1930s (PE21/10), but this word is probably best avoided, as it clashes with Q. lindë “singing, song” (PE17/80).