1) Ask something simple, like FizzBuzz. You'd be shocked at how many people talk a good talk but can't actually write basic code.
2) Ask an open-ended question, like "how would you design a multi-player chess game". That leads to a discussion that lets you assess all sorts of traits, the most important of which is communication style.
In this analogy, you are the company hiring programmers, and the things you need to survive are that your programmers can write basic code, can communicate effectively, and some other things — probably "can design software" or "doesn't rathole excessively" is the next item or two on the list. You're still in a lot of trouble if your submarine doesn't have any food onboard, but the situation is not nearly as bad as if the submarine lacks means for producing air and drinking water.