"Fine as frog hair" is a colloquial phrase that refers to feeling well or having a good day. However, there are several other synonyms to describe an individual's current state of feeling. One may say they are "tip-top," "hunky-dory," "fantastic," "excellent," or "splendid." Alternatively, they could be described as "in great shape," "doing well," or "on top of the world." Additionally, some could use the phrase "feelin' groovy," "livin' the dream," "winning," or "rockin' it." Overall, there are plenty of phrases and words to replace "fine as frog hair," depending on personal preference and the situation's context.