Come hell or high water means to tackle a difficult situation no matter what the hurdles or problems. It refers to the fact that both the proverbial hell and actually high tides can be tough to face.
1. Despite her busy schedule, Vandana decided to reach the Platinum level of membership at ISC before year-end come hell or high water.
2. Kumudini woke up with a slight fever but nevertheless aimed for the archery gold medal come hell or high water.
3. When the doctor diagnosed Mrs. Patkar as having cancer, she vowed to fight the disease come hell or high water.