You will have room to store whatever you want to store for 10 days outside of the freezer. If you have ever changed out or serviced a boats freshwater system you will never drink from one again. I am lazy so I brush my teeth with it. Our group will always have small bottles in the heads for those that want to brush their teeth with a clean water source. We always have bottled water available for those that want it plus at least one gallon per person to wash with if the freshwater system ever fails. The moment you are out of water. Here is your gallon to use until we sort this out. I would not sweat this. Have the water you want delivered and be done with it. Most groups will be getting some or much of their water when dining out. Meals ashore are a great hydration time.