Super Mario World/Soda Lake
You have found what is probably the hardest level in the game. It is an underwater hidden level that can only be found through the end of the Cheese Bridge level. However, if you try to go over the normal exit, it will count as beating the level and you will not be able to access this level. Soda Lake is the only level in the game with Torpedo Ted, an underwater Bullet Bill. Watch out for the exclusive Torpedo Ted; watch their movement, crouch and run. They are indestructible so just finish it and you are off to Star Road. If you beat this level, you will unlock a star world warp.