"In dire straits" is an English idiom referring to someone who has somehow come to be in a very serious predicament. The implication with this phrase often is that the person or persons who find themselves in such a situation may not be able to extricate themselves from it. As a result, there is a serious undertone that often accompanies the usage of this phrase. Seafarers who had to pass through dangerous waters were the originators of this phrase.
Sometimes speakers choose to describe ideas or feelings in very clear, literal terms. Speaking in this manner can become stilted and unexciting after a while, though. As a result, many people use short phrases known as idioms, which may have meanings that are accepted by a specific culture even if they differ wildly from the literal definitions of the words that they contain. These idioms are perfect for those people who want to sound more colloquial and impactful in their speech. One such idiom is the phrase "in dire straits."
The accepted meaning behind this phrase is that the person being described in this manner is in a lot of trouble. Circumstances have arisen which leave someone in a desperate situation from which there appears to be no available remedy. As a result, a phrase that conjures up such serious images is necessary. For example, someone might say, "I can't believe that the plane is out of fuel, and I'm afraid now that all of the passengers are in dire straits."
Of course, the phrase is flexible enough to be used on less somber occasions. Using it in less serious situations implies that there is a bit of exaggeration being done by the speaker. The problems being faced might not be life or death, even if they are particular damaging in their own specific circumstances. As an example, consider the sentence, "I thought our team would be able to come back, but it looks like they're in dire straits now."
In that last example, a relatively trivial occurrence is described in a dramatic way. Such exaggeration gets to the heart of what idioms are meant to accomplish. If this particular phrase were taken literally, it would mean that everyone described in this manner were in danger of drowning in dangerous waters. Instead, it is accepted that the idiom "in dire straits" refers to a problematic situation that can occur anytime and anywhere.