Having a fixed way of solving a puzzle is also fine. I would not say that this is wrong or not good, it's a design choice :) I think making it a bit more fair like maybe having a bit more water than needed to toy around a bit and not get stuck because you "wasted" a tiny bit of water would be a good idea. Or maybe adding a health system, so you don't die immediately. Random idea: Instead of killing you directly when you touch a fire maybe just increase the heat bar in a fast way. This way the player can still escape or even run through a single fire and use the water to cool him down. There is definitely potential in your game. And fire fighter much cooler than the devil :D
Thanks. I'm glad you enjoyed my game too!