plunge

An act of jumping or diving quickly into water or a deep place.

"He took a refreshing plunge."

To fall or jump quickly and suddenly into water or a deep place.

"He plunged into the cold sea."

A sudden, rapid fall or drop in value, amount, or level.

"The market saw a sharp plunge."

To decrease sharply and suddenly in value, amount, or level.

"Share prices plunged dramatically today."