What does the saying "Hell or High Water" mean?

It usally means "no matter what" and it usally starts with the word come as in come hell or high water. Ex: "I will be there come hell or high water." they are just saying that If hell rise's up to get in their way they will be there. If a flood come's to get in their way they will still be there. You must not live where it flood's very much. Here we are alway's flooding.