"Black' water

I was playing Tomb Raider 2, using the Cheat Engine to find some cheats for fun and all of a sudden the water in Lv 1 and Lv 2 turned all black without transparence. I was unable to get the key in the under water tunnel in Lv 2. I can't figure out what the problem is.

I tried emulator version 1.7 and 1.8. The results are the same. I also tried different gamesaves and isos. I had no goal. Please do give some help!