Watch Out Below! is the second level of the games Super Mario World 2: Yoshi's Island and Yoshi's Island: Super Mario Advance 3. It revolves around falling giant Chain Chomps. It also introduces the endless pits to the game.
As the level starts, Yoshi finds himself on a field. Upon moving a bit to the right, the player notices a sign with a Chomp head on it. Upon looking to the background, the player must notice a small Chomp. After moving a bit more to the right, this Chomp jumps in direction of the player, finally falling down and creating a pit. This pit, logically, makes the player lose a life. After this quick encounter, the player has to dodge the rain of Chomps the level offers, at the same time he or she tries to collect Special Flowers, red coins and other things. After a while of dodging, the player goes through some Flippers and enter the next section of the level. After going through the middle ring, which "saves" the player's progress until he or she loses all of their lives, the player has to throw eggs at the walls for them to be destroyed. This way, Yoshi can go on and get out of the short, semi-underground area. After getting out, Yoshi has to go through some caves until he reaches a Helicopter Bubble. When touching it, Yoshi morphes into a Yoshi Helicopter. Yoshi must race all the way to the Yoshi Block (and collect coins and Special Flowers in the process) and continue his way. After going through a pipe and encountering one last Chomp, Yoshi reaches the finish line and give the Baby Mario to the Cyan Yoshi.