With kitesurfing you also have the lines in the mix. The biggest waves I personally surfed were 8m (what can I say, I was young and stupid). One guy dropped his kite and the next thing he was standing on the shore with every section of his kite ripped out. We were all feeling sorry for his ruined kite but he was happy to get out of there alive. Apparently he got tangled in his lines underwater and thought he was done but by some miracle managed to get out.