Hi Harald,
I'm not sure if my post helps or not. I also tore my achille's tendon about 6 years ago. The doctors had a hard time deciding what was wrong with it until about 2 years ago, so it was never properly treated. I didn't have the cast, just crutches, as I had also torn all the tissue in my foot and damaged the knuckle joint on the top of the foot (gotta love Thoroughbreds). I do exercises to keep the elasticity in the tendon, and as long as I don't go running every day, it usually does not affect me. It has yet to affect me in the water *knock on wood.* We dive about 3 times a week, and just as a precaution, I am careful with tricky entry points, but haven't yet had a problem.
Good luck and I hope you heal!
