Tap the left and right arrow keys. Try to get the bar on the red line. The red line will move up, so you will have to tap faster. The closer you are to being on the red line, the faster the cog withh fall into the water. However, the cog can also pull YOU in if you're not tapping fast enough!
If there are four toons playing, sometimes you will be put on the side that the cog is usually on. You'll have a big head (which will go away when the game is over) and the other toons will try to pull you in. You need to pull them in first!