If you deal with a difficult situation with aplomb, you deal with it in a confident and skillful way.
If something plummets, it falls down from a high position very quickly; for example, a piano can plummet from a window and a stock value can plummet during a market crash.
measure the depth of something
a craftsman who installs and repairs pipes and fixtures and appliances
thrust or throw into
Differentiated vocabulary for your students is just a click away.