He dived in after her without a second thought.

他不假思索地随她跳入水中。

This murderous lunatic could kill them both without a second thought.

这个杀人狂会毫不犹豫地把他们两人都杀掉。

Please have a second thought.

请再考虑一下。

Then they fire them without a second thought.

然后，他们会不加考虑，就把他解雇。

A: I hope you'll give a second thought to it.

希望你再考虑考虑。