An adjective for “deep” in The Etymologies of the 1930s derived from ᴹ✶nūrā under the root ᴹ√NUR of the same meaning (Ety/NUR).
Qenya
tumba-
verb. to cast down (into a pit[?])
tumba
adjective. deep, lowlying
núra
adjective. deep
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.
The verb ᴹQ. tumba- appeared in a marginal note to a rejected page of verbal roots in the Quenya Verbal System (QVS) from 1948, with the somewhat difficult to read gloss “to cast down (into a pit[?] etc.[?])” (PE22/127). It was derived from the root ᴹ√TUB meaning “go down, below normal ground-level, esp. to go down (sink, dive) into water”. The other derivatives of this root, adjective tumba “deep” and noun tumbo “deep valley”, continued to appear in Tolkien’s later writings.
Conceptual Development: A possible precursor to this verb was ᴱQ. tum or tub “dive” in Early Qenya Word-lists of the 1920s (PE16/132), which in turn was likely derived from the early root ᴱ√TUM(B)U (QL/95) as suggested by the editors.
Neo-Quenya: I would retain ᴺQ. tumba- for purposes of Neo-Quenya as a weak verb based on the adjective tumba “deep”, with the original sense “endeepen = go (or cause to go) deep”, hence with transitive meaning “cast down (into depths)” but also intransitive “dive”.