After getting our new dog Jonas, a 5 year old german shephard / grayhound mix, I waited for warmer weather before taking him out on the kayak. He sat in my lap and was fairly concerned about everything, but was having a good time by the end of the trip. I decided to build him a platform that he could sit, stand, or lay on. I built a prototype out of some scrap wood and it ended up turning out well enough that I did not have to remake it.
Here is a video of the finished product:
I wanted something that was easily removable but still attached enough the he could jump around on it without capsizing us both. I didn't take too many construction photos but here is what I ended up with at the first test fit compared to it with the carpet installed and handles cut into the sides. I utilized the elastic cords on the kayak (the black cords that you see) and cut some slits through the platform that I could feed them through. Then I looped the cords over the ends of some low profile screw heads to securely hold the platform down and pull it into the back of the seat which acts like a lock.
The first test was a success. I did notice that the rear corners touched the water when I would lean. Thankfully they extend below the platform so I was able to taper a cut that would stay level with the water. This also eliminated the water that you see in the back of the platform.
You can see how much more clearance I get with the tapered cut. He can even stand in the rear corners and unless I lean that way, they do not touch the water. Kayaking has been much more fun with him on board and it cracks me up to see him dive off the platform chasing ducks. As you can tell, he doesn't like it at all.
The platform should also work well the next time I go kayak camping. Especially for things like a cooler or items that have a hard time fitting inside the kayak.