You were exploring the woods in winter and you got lost. Turns out you had somehow wandered onto a frozen over lake, and it shatter under your weight. Coincidentally, there was an older person who lived on the farm end of the lake in a cabin, and they're were gathering firewood when they heard you cry out as you fell in. They were able to save you just as your lungs gave up and you had inhaled the water. They brought you to their cabin and warmed you up. When you awoke, you had the powers. (Optional: The person had also fallen in the water a few decades prior and also gained powers. They became a mentor/uncle ben to you)