So many people, so many boats, so many conditions. Over the years kayakers have tried many different ways to help each other back into their boats. They have learned which ones work in each situation.
I refer to these as advanced rescues not because they are more difficult or require more skill or strength, but because we tend to teach thing like the T-rescue first. We have to start some where and then move on from there. So if you take more training (to become an instructor or guide for instance) you will learn some of these. And then you will be an advanced paddler!
Using a Rescue Stirrup
This video provides a good overview of how to configure and use a stirrup to help you re-enter a kayak on your own or with assistance. The demonstration uses a sit-on-top where the paddle is positioned at the front of the cockpit. For sit-in kayaks we position it just behind the cockpit.
The exact method shown here takes a minute or two to set up, but it really holds the paddle in place firmly. This should work well on wider recreational kayaks that might not have suitable deck lines on the back deck.
This is a very good lesson from the folks at BodyBladePaddle on how to get a person back in their boat very quickly. Commonly referred to as "the scoop" rescue, it is another way of dealing with people who can not climb in to their boat. It even works if they are injured or lack the strength required to climb on a tall boat.
It also introduces the idea of using a paddle as a lever, which I have not seen anywhere else.
"Cowboy" self rescue
This video calls it a "ladder", but on this side of the Atlantic it is called the "cowboy" re-entry.
Although this is fun to try in sheltered conditions I would not recommend that you consider this a part of your emergency plan. Although they actually demonstrate this in rough water it is important to realize that they are using an classic British boat that appears to be empty.
I would not try this in a boat with a rudder!
Paddle Float With Stirrup
As stirrup can also be used with a paddle float for a self rescue. There is no narration, but if you watch closely you can see what he is doing. There is quite a bit of gear that needs to be set up.
While we often think of this as a technique best suited for people lacking upper body strength I think we should also keep it in mind for injured or exhausted paddlers.
The Hand of God Rescue
This technique addresses the terrifying prospect of someone trapped in a capsized boat. This could be the result of panic, a tight spray skirt, a leg snag or medical incapacity.
The "Hand of God" in this case is you, the rescuer, reaching down and lifting them up. It is actually not as hard as you might think if you press down hard on the near side. You also need to grab their PFD and push back as well as pull.
Another way to deal with this situation is to reach under to release the spray skirt and then pull them out of the kayak.