The new students were just left to sink or swim.

学校完全让新生自生自灭。

I think athletes sink or swim depending on how they motivate themselves.

我认为运动员的成败取决于他们如何激励自己。

This time he'll sink or swim.

这回对他将是成败在此一举。

This is a sink or swim situation.

这是一个不计成败的情况。

Sink or swim, he must try.

成败劝靠自己，他必须尝试！