"plunge beneath" is correct and usable in written English.
You can use it to mean to dive or submerge into a lower level, such as water, snow, or sand. Example: The boy plunged beneath the waves and swam beneath the surface of the lake.
Then Dr. Tinker, watching with binoculars from the boat, sees her awaken and plunge beneath the surface.
The karst regions along some spurs of the Greater Caucasus contain rivers that intermittently plunge beneath the earth into caverns within the soluble limestone bedrock.
They commonly are deformed into a fold and thrust belt as the basement under them continues to plunge beneath the overriding plate at the subduction zone.
And he proposed to himself a plunge beneath the surface of the visible, the creation of a detailed world wholly inaccessible to the naked eye.
While spines continually plunge beneath the level of the waist, legs kick explosively above it or maintain powerful extensions like searchlights.
Robert Kitson Giovanbattista Venditti (Italy) His try against Ireland was not the most beautiful a right wing could score; more a plunge beneath bodies from a foot out.
The largest earthquakes threaten people who inhabit regions where one plate plunges beneath another.
That amounts to an area larger than Manhattan plunging beneath the sea annually.
Soon as I went in and plunged beneath the surface a shock of cold clawed at my lungs.
Instead, the leading edge of the descending continent is scraped off, and the rest of the continent then plunges beneath the off-scraped slice.
Just off the coast, the Nazca tectonic plate plunges beneath the South American plate, pushing the towering Andes cordillera to ever-higher altitudes.
