This is a very handy water bottle for kayaking. It's a very simple nylon bag with rubber lining in 4l capacity. The drinking tube is sold as an additional item.What I liked about this compared to the Camelback or similar products was that this one is simply a water bladder. I'm not paying for a backpack style that I won't use. This allows me to store the bottle behind my seat in the cockpit. This keeps it out of the sun and cooler than on deck or on my back with other styles.
I found that 4l is plenty for all day, it's a larger capacity than most other products. This setup comes in at approximately $40-$60 cheaper than the backpack types.
A couple tips; run the drinking tube up inside the skirt tunnel to have it handy, and also secure the bag using its nylon webbing straps to the seatback or backband using a cheapo carabiner so it won't disappear when you dump out.