Getting that gem is hard, water seems to always get there too fast. quality video/music

I don't mean to incite a mob, but getting the gem might be luck based? The only action involved in rising the water is those crates you fall through, and there's only one way to fall through all those crates. The lag which comes after hitting the crates varies in severity so that might have something to do with it. I don't know enough how the game works to know whether or not there's a trick to that part.

You also have to move really fast in the parts before and after the gem to still beat the cave. That's why I'm jumping over crates and such at 0:37, to ensure I can grab the gem and reach all the treasures in the gem room before they fall. Also why I fly through the YAYA logo afterwards. If you got the gem and tried to go through the level at a more regular pace, you'd probably get stuck at the stack of crates near the five treasures in the bottom right or the stack of crates near the extra life.