I make sure to take a bottle that has a relatively wide opening so that I can put ice into it easily. Nothing better than to get back to the ship after a hot day, fill the bottle with ice and continue refilling it with water until the ice melts completely. I don't generally carry it around with me so that's not an issue but if you like to do that, you'll want one that's easy to carry or has a carabiner or clip that allows you to go hands-free.