Thank you @Dizzi-Tired and @Onandon03. The exercises look very straightforward and I’ll give them a try. I also usually swim for 30 minutes, but I’ll take up your advice and try for less once it is warmer here.
A friend of mine came up with the idea of getting some juggling balls and learning how to juggle. And I saw an interesting video on playing table tennis by myself. Here is a link: https://www.youtube.com/watch?v=i8Pv8vWdyL8
I think both the juggling and the table tennis practice will also help with my rehab. I’ll let you know whether they do.