Theheart rate rises initially, then plummets.

心率先是加快，然后大幅减速。

During the days when I don't do that, my productivity plummets.

我不这样做的那段日子，我的生产率骤降。

Deep and narrow, the bay plummets more than 8, 000 feet (243 meters).

深而窄的海湾，大幅下跌了8,000英尺(约243米)以上。

If this happens, the value of the semi-precious stones plummets.

如果发生这种情形，半宝石的价值就一落千丈。

Deep and narrow the bay plummets more than 8 000 feet (243 meters).

深而窄的海湾，大幅下跌了8 000英尺(约243米)以上。