We're moving to MN this month and will be paddling in the icy waters of Lake Superior occasionally.  I installed a Rule 1,100 gph bilge pump to help pump water out of the large cockpit if we ever capsize.  

 Here's a view from the cockpit.  The four stainless bolts hold the Pelican box to the aft side of the bulkhead.  Water exits the port side.  I installed a simple cam plug to keep water from flowing into the cockpit from the deck.

View from stern.  Notice the pull switch on the starboard side near the bungee cord.  

Pelican box installed to bulkhead.  Notice the bottom side of the switch and the wiring coming through the bulkhead from the pump.

Battery and fuse fit nicely in the Pelican box.  This is a secure means to store the battery and nothing will come loose if the kayak flips upside down.  The 5.1 amp hour battery will run the pump for over an hour.  Perhaps overkill, but it fit inside the smallest Pelican box.  I'm not concerned about extra ounces on this project.  

Final Thoughts

Others have installed magnetic switches and relays.  I opted to keep this as simple as possible with a good quality, marine, on-off switch wired to the pump.