dive

verb:to plunge headfirst into water, especially as a sport
- The athlete will dive from the high platform into the pool.
verb:to go quickly to a deeper level or lower position
- Stock prices began to dive after the unexpected news broke.
noun:a plunge into water, especially headfirst
- Her graceful dive earned her a perfect score from the judges.
noun:a sharp downward movement or fall
- The stock market took a sudden dive this morning.