The phrase "hell or high water" is a common expression used to refer to challenging situations that require resilience and unwavering determination. There are several synonyms for this phrase that can be used in place of the original expression. Such synonyms include "come rain or shine," "through thick and thin," "no matter what," "at all costs," "unwaveringly," "in good times and bad," "regardless," "unconditionally," and "undauntedly." All these synonyms have the same meaning as "hell or high water" and can be used interchangeably in any context to convey the same message of determination and perseverance in challenging situations.