Yes, plunge is a Scrabble word!

Verb

1. Thrust or throw into

2. Drop steeply

3. Dash violently or with great speed or impetuosity

4. Begin with vigor

5. Cause to be immersed

6. Fall abruptly

7. Immerse briefly into a liquid so as to wet, coat, or saturate

8. Devote (oneself) fully to

Noun

1. A brief swim in water

2. A steep and rapid fall