I find that the CamelBak Podium Bike Water Bottle are great to have with you in the kayak. The cap has a locking mechanism with a one way valve, so salt water cannot intrude into your bottle and ruin your water supply. These bottles can also be wrapped with the waterproof Velcro tape to ensure they stay attached to the bottom of the cockpit and will not roll around when you are kayak surfing or get lost if you have to do a wet exit.
As an Amazon Associate, I earn a commission from qualifying purchases.