Look for the terms like DCS or Taravana in the search function - there are several threads with important information. There is also one thread containing decompression tables for freediving. Better told, they do not show decompression time, but rather recommended surface time beteen dives in fucntion of depth and time spent down.
Freedivers like Eric Fattah reported bends at repetitive dives to relatively moderate depths. And there were also already some accidents - look up Carlos Coste or Benjamin Franz
You can get some information also here
DCS @ APNEA.cz