A strait is a narrow sea channel or a difficult situation — remember that both are difficult to navigate. If you're stranded on a strait off the Black Sea, you might also say that you're in dire straits.
The noun strait comes from the Latin word strictus, meaning "to bind or draw tight." Whether you're describing a narrow passage of water or a tricky situation, a strait will make you feel like you're in tight quarters. You might be familiar with the term "dire straits," which refers an urgent or drastic situation. If all the dorms are overbooked for the fall semester and the off-campus apartments are all rented, you might find yourself in dire straits.