A good size to bring is one that is 3 or 4 inches long – the carabiner will need to clip through the loop on your Nalgene water bottle and the 1-inch strap on the raft. This will make it easier to access your water bottle throughout the day.
They do not need to be super heavy-duty climbing carabiners. Also, you probably do not want one that has a twist lock or sleeve on it because it can be a hassle to open and close.
Carabiners can be found on our online store or REI.