Attached a savegame from directly afterwards, just place it in your SOMA save folder (if you turn around and go back the ladder you can get in that area again if you want)
Though I did choose to kill the WAU in that one so if you made a different choice it might be better to try it yourself.
In case you want a strategy, I did it similar to what caffeine4671 described and lured the monster in a circle first before running for the second airlock door and hiding in the room near it, waiting for it to open.
Side note: This was the first and only time in the game where I died
He completely surprised me after that first airlock opened so he got me right there and then I ran down the corridor in panic, only for him to decide to chase me again a few seconds afterwards, completely finishing me off.
Well played Frictional Games, well played