I just encountered this problem. Horrible graphics glitches after the flood scene. Sound did seem to work. I could slowly move around a tad and then my Mac Pro crashed and restarted. Afterwards, I found that Steam had forgotten my login and where my Steam folder was. I fixed that easily, but my SOMA saves seem to be gone now. When I start the game there are no saved games to load (the option is greyed out). I assume they still exist but SOMA has forgotten where they are.
Up until that point, everything seemed to be going well.
Mac Pro Late 2013
64 GB RAM
3.5 GHz Xeon 6-core
2xAMD FirePro D500
Edit: Ah I see the Mac Pro thread. It doesn't seem to mention the Steam folder and saved game problem, but otherwise it's the same issue.