I deleted the CellsCache and i got the f**k away from the grand reef and the lag stopped. I'm too scared to go to the Grand Reef now as I lagged my tits off when I tried entering it which was the reason of this post in the first place.
I've tried switching to experimental mode and nothing changed except for beacon icons. Lag is still there (1FPS). I am seriously frustrated about this lag issue. It renders my game unplayable. Do i need to start a new game to finally play Subnautica…