I want to share with you an experience that shows how incredible are tortoises.
It happened that just behind the yard where I have the Russians there is a pond with a pair of aquatic turtles.They was a piece of wood sepparating them, buried but not deep enough. One day I saw with horror that there was a tunnel communicating the two sections and a russian swimming in the pond. They can swim. It was in the midday at two o´clock. I rescued it and put stones into the tunnel. About 4 o´clock I was wondering if one of the aquatics had gone through the tunnel to the Russians section, so I used a stick to explore the deepest part of the pond. I touched something that look like a rock. It was a Russian. I took it out and it had the neck completely extended and the eyes wide open, unreactive. I felt quite guilty and then,I couldn´t believe it, he blinked. It wasn´t dead. Seconds later it breath once. About 6 o-clock it was as normal as the others. I know for sure it was underwater for two hours, but I don´t know how longer. The only explanation is that it was early spring and the water was cool. It reduced it´s oxigen needs and it survived thanks to anaerobic metabolism. That´s why any veterinarian induces anaesthesia in tortoises with inhalated gas. Next day it was eating normaly. I like Russians, they are incredible animals. And incredible diggers. And they can swim, but not for too long.