Take the plunge 冒险尝试
动词 to plunge 是往下跳的意思，比如：When we arrived at the lake, my brother plunged into the cold water.
短语 take the plunge 往往用来形容我们下定决心做某件高难度的事情。
I'm going to take the plunge and move to France. I've been dreaming of it for years and I'm finally going to do it!
My brother is going to take the plunge and quit his job. He's been meaning to leave for months.
Let's take the plunge and buy a house!
另一个从跳水运动演变而来的表达是 to dive / jump in with both feet, 两只脚一起跳下水。这个表达的意思是很快全身心地投入某件事情。
Rachel jumped in with both feet when she started her new job. She learnt everything very quickly.
When I started English lessons I dived in with both feet: I practised every day and rapidly improved.