"Up the river" is a phrase that describes being in a difficult or challenging situation. There are a number of synonyms that can be used to convey this idea. One option is "in the hot seat," which means being under intense scrutiny or pressure. Another similar phrase is "in deep water," which implies being in trouble or facing a difficult situation. A more dramatic option might be "up a creek without a paddle," which implies being in a hopeless situation with no chance of rescue. Alternatively, "up against the wall" suggests being cornered or faced with a difficult decision. Ultimately, these synonymous phrases all convey a sense of difficulty and challenge in navigating a given situation.