My perspective: I'm a working sea kayak guide in Atlantic Canada, in an area with a heck of a lot of granite and intertidal slippery sea weed areas. I take the choice of my footwear very seriously. My footwear not only keeps me safe, but my guests as well. Confidence in my grip is essential to me doing my job.
So with that, I give these paddling shoes a 9. They are better than most that I have tried, but still do not give me the same 100% confidence that I have with my very old, very glued back together Nike ACG Mid Tokatees (unfortunately, not made anymore!).
That said, the Son-R Buckle is a solid piece of footwear. Well made from what I can tell after initial test run. What I really like is there versatility. This could be one pair of footwear for a summer sea kayak trip. Both good in the boat, then for an adventurous island hike, as they have good support and feel on land and in water. Probably fit about a 1/2 size too big if you are just bare footing in them, but about right if wearing over a bootie or drysuit. The buckle seems solid to me, and think they would not come off at all in whitewater river swim (haven't tried yet though).
I look forward to getting good use out of these, as they are great in the summer, allowing my feet to breathe a little more too. Certainly better grip than any sandal that I have tried around the water, and they fit very well in my kayaks too (touring or ww). My one caveat is on the grip. While quite solid in comparison to many others on the market, I'm still unfulfilled in my ongoing quest to hopefully one day retire my old Tokatee's. (or until Aquaseal can't keep them together any longer....)
Very stable, well sized, great features. Much like what Eric Jackson has done for kids in whitewater boats, the SP fills an awesome gap. In reference to the seat support, it has the more advanced backband of higher end kayaks vs the high full seat cruiser. Yes, a personal choice, but the outdoor/athletic kids I had just loved it. Can't wait to teach one of them to try a roll in it!
The one area that I had a bit of trouble with is that the seats are closer together than some doubles. This really puts the onus on paddlers being in sync with one another. If you can do this, then you will be fine. Could be more of a challenge with taller paddlers, well, paddlers with longer arms. This is going to be a negative with a double that comes in at 16'6".
The other alternative, to allow more paddling arm room is the Carolina Perception Tandem, but then the stern seat is so far back, it rides with the bow way up with different weight paddlers.
The Polarity also shines as a kayak for you and your child! It is very easy to control and paddle the boat from the stern seat no matter what the bow paddler is doing. This, combined with the weight savings of a shorter tandem, make this boat very easy to handle. I can lug it around by myself without too much problem (sure, I do this for a living, but you get the point. There aren't many other doubles that you can put up on a roof rack by yourself if you know what you are doing).
My rating of an 8 is really an average rating for the boat. The rating moves up if you are buying the boat for the right proposes... and down if you know you and your partner cannot paddle in sync! Thought we were going to have one divorce out on the ocean over that one time too!
On the down side, it's big and heavy, but that gives it stability. Also a small person with short legs might have difficulty operating the foot controls fully for the rudder, as it is a wide boat. You can rig it up to allow a little more slider room if you know what you are doing.