When you kayak camp it is often to a remote location (true primitive camping). Although the trip involves paddling through a lot of water - of course - it is not potable due to the salinity of the ocean and creeks in SC.
The recommendation is to carry a minimum of one gallon of water per person per day. Although there are many options available to transport water, I have found the MSR dromedary to be the most user friendly.
I have a 10L, 6L, and 4L. Check them out on the next coming trip - I'll demo show they work!