I recently bought the TK11 R2 and took it caving with me.
The light is impressively bright and throwy as you know, but it was also very resilient. I spent a few hours climbing and crawling through tight tunnels, through water, with it either holstered on my belt or in my hand (with supplied lanyard around my wrist) and the TK11 stood up to it all, no problems.
Just washed the mud off in the sink when I got home and it was good as new. No water or mud ingress into the light whatsoever.
It seems to live up to the "Tank" designator.