I never knew the GG version had this. I wonder why they used the crappy effect with high priority dithered tiles if they could use what the Genesis/MD games use. On the other hand, Sonic 1 SMS also combined both types of water... GHZ has the dithered tiles and LZ had the palette change. They probably wanted to have water pools at different heights. But it's still a mystery why Sonic 2 on the GG has the rising water while the SMS version doesn't.
It's a long shot, but maybe since the Game Gear version's screen is smaller, there's less stuff on it at a time and therefore more visual ram space to work with and not experience slowdown. Also, the GG version is pointlessly missing the speed shoes, maybe they took them out to make even more room for the rising water effect?










