Emptying a swamped whitewater kayak is slightly different from emptying a swamped sea kayak because the boats are much smaller and more manageable, and because the shore is often much closer. Still, a little technique can make a big difference.
If someone in your group has gone for a swim, you have two choices: you can help them get to shore with their gear, or you can perform an on-water boat-over-boat rescue. Both of these options will be MUCH easier if there are float bags securely tied into the stern of the kayak.
When you go to empty a boat, look around for any potential hazards. Also make a plan for where you want to take the boat once it’s emptied; that may be close-by, so you don’t need to empty much water or you may need to completely empty it for ease of towing it a longer distance.
Before you start make sure you’re comfortable with the location and not putting yourself in any danger. The first step is to get next-to and parallel-with the upside-down boat, bows facing in the same direction. Next, reach under the boat and grab the cockpit rim with both hands, flipping it up on its edge and slowly raising it, emptying as much water as this allows.
Once you have emptied as much water as you can this way you want to flip the boat over your bow and rock side-to-side until most of the water is out of the boat. Now, quickly flip the empty boat off your deck and either push it where it needs to go, or clip onto it with the tow tether (cowtail) attached to the quick-release belt on your rescue life jacket.
Make sure that after you read about how to perform this skill or watch a video that you go out and practice with your paddle buddies. Start off in calm water and work your way up to more challenging scenarios to practice in.