Says what it is. Eat 1000 sharks. When you read this you might think to yourself "Well that's easy, I'll just replay the last level and keep eating the big evil shark guy". Apparently that doesn't count. Yes, it will show up in your foodbank I believe, but it doesn't count towards this achievement (from everything I've read). Therefore, if you're going to want this achievement, you're going to have to replay levels. Note: You must finish the level you're on for the sharks eaten to count towards the achievement (running out of all lives/continues will prevent it from registering).
1) Combine this achievement with 10 Hours, Frenzy Fanatic, and Shark Eater.
2) You can do one of two things. You can either just keep replaying through the game or you can keep replaying certain levels. I recommend altering between the two to make it less repetitive.
3) Start by working towards "Shark Eater" by replaying a level with Sharks in it. I recommend one that has "Mines" in it so that you can kill yourself before you beat the level so you can eat some more sharks with your plentiful lives. Level 37 is a good level to do this on. NOTE: YOU MUST BEAT THE LEVEL TO HAVE THE SHARKS COUNT TOWARDS THE ACHIEVEMENT. DO NOT LOSE ALL YOUR LIVES BEFORE BEATING THE LEVEL.
4) You don't get points in your foodbank while playing Time attack mode, so make sure you're in adventure mode.
Credit to lozzy for the sweet video which he linked in the comments and uses in the walkthrough.