A couple of years ago when the kids all started using hydroflasks (or reusable water bottles) we decided to get rid of plastic water bottles on our boat. It has been one of the best decisions we have made! Everyone has a nice cold water, they can keep track of how much they have drank, refill it throughout the day, and it will keep it cold for hours. No more half drank warm water bottles all over the boat that no one will claim. We all love our hydros and have them decked out in stickers from everywhere we have been, they look like a postcard of all our travels. We love getting stickers for them, especially our Lake Surfer ones!
I keep a couple of gallon water jugs in our freezer and when we are going out on the boat I put one or two in our cooler (depending on how long we are planning on being on the boat for the day) it acts as a block of ice and as it melts is ice cold water. I also keep a bag of crushed ice in the cooler to refill and extra gallon water bottle in the cooler if there is room or just on the boat to fill up when needed. We keep at least 3 or 4 gallons of water on the boat for a day trip, the most we have ever gone through with ice is about 2 but I would rather have more than not enough. I try to make sure all our guests know beforehand to grab a hydroflask, and I also keep an extra on the boat. I store about 6 water bottles on the boat in case.
When we are on a camping-boating trip we bring our 5 gallon insulated water cooler that leave at camp fill it with a bag of ice and water and have everyone fill their hydros for the day. This system saves so much waste on plastic, the half drank waters, and I love how everyone can keep track of how much they have drank. Keeping everyone hydrated after wake surfing, swimming and playing in the water is hard to keep track of, this system has helped us, and I like to think the environment a little bit too.