I read what you wrote on the blog about biking and surf mats in pools which also struck home. I don't often get to actually surf on the mat and when I do, my arms are usually shot in short order. So last January I started training in my local community pool - with the mat. They weren't going to let me use it at first because they have a rule against inflatables. I explained to the pool manager that I was training for surfing. After he heard my explanation he said he would allow me to use the mat. I've been training basically 2 to 3 days a week there ever since.
The interesting part is that I've had two people, on separate occasions, who have wanted to try the mat in the pool. One was the pool manager and the other was a professional triathlon trainer. Both of these people are experienced swimmers. They both had exactly the same experience - after one lap (50 yards) they were exhausted! Their arms were shot. I was really shocked. I had always assumed that swimming would be a great conditioning exercise for surf paddling. That does not appear to be the case (I guess it's akin to running conditioning not being really helpful for hiking long distances.)
This also comes to mind: I started mat surfing a little over a year ago. (I already knew how to surf with a board before trying the mat.) So far, it seems very natural to me to be on the mat, surfing. I can control the mat and go where I 'will' it to go. I honestly can't explain exactly what I do to control the mat. I ride a mountain bike every day to work and back (about 2 miles each way). I ride no matter what - rain, and snow unless it's too deep. In the snow you really have to be conscious of your balance - minor weight shifting in the wrong place or wrong time can be unhealthy, ie; you fall. Somehow I think the weight shifting/awareness in the bike riding has helped my mat riding. Just a theory, but it's the only way I can explain why surfing on the mat seems so natural to me.