Alternately: Enemies in the same place at the same time, especially facing a common danger, challenge, or foe. People who would normally fight, forced by circumstances to work together. Being in the same boat.
Notes: This is a famous compound dating from the Spring and Autumn Period of Chinese history. If people from rival states Wu and Yue found themselves riding on the same boat, it goes, they would be constrained from fighting for fear of harming those around them, or damaging or capsizing the vessel itself. In fact, if a storm were to arise, they’d be forced to work together in order to survive. Similarly, if rivals within a foundering company or politicians from opposing factions within an endangered nation set aside their differences to work together, they’d be in a state of 呉越同舟. Wouldn’t that be nice?