We need water to survive. Water is not an option for us. Our lives depend on it.

Jesus said to the woman at the well,

"Everyone who drinks of this water will be thirsty again, but whoever drinks of the water that I will give him will never be thirsty again. The water that I will give him will become in him a spring of water welling up to eternal life." The woman said to him, "Sir, give me this water..." John 4:13-14 (ESV)

Here is a delightfully probing workbook delivered by two highly regarded Christian mentors...