[gwbas1c]

https://www.google.com/search?q=sink+or+swim&ie=UTF-8

(In case my results are personalized)

> "Sink or swim" is a common English idiom that means a person must either succeed through their own efforts or fail completely, with no middle ground or outside help.

There are a lot of jobs in the US that are easy to get, but many people fail at the job. Typically these are sales jobs where the pay is mostly commission. (IE, most pay is tied to making sales.) The "sink or swim" aspect is that either someone is successful (IE, they make sales and get paid) or fail (don't make sales and thus don't get paid) and move on.

[TeMPOraL]

Right, but I understood this to mean you either succeed at this job, or fail and go do something else. Succeeding or failing at individual sales isn't particularly interesting- broken down enough, every job has binary outcome subtasks.