"Hook line sinkers" is a phrase commonly used to describe a situation where someone is completely enamoured and invested in something. There are several synonyms for this phrase that can convey the same meaning in a variety of ways. "All in," "fully committed," and "completely dedicated" all capture the essence of the phrase, highlighting both the depth and sincerity of one's investment in a certain activity or pursuit. "Hooked," "captivated," and "enthralled" are other useful phrases that signify complete devotion and captivation. Regardless of which phrase one chooses, each conveys the idea of being completely and wholeheartedly invested in something.