Instructions
Unlock "That's What I Call Teamwork!" by playing all 42 of the Free Play levels with at least one other player. The players are only required to play through each level from beginning to end, regardless of their final score. However, this achievement can be combined with the "Platinom Nom Nom" achievement.
Unlock the "Platinom Nom Nom" achievement by earning a platinum medal or by playing with someone who earns a platinum medal in all Free Play levels. This achievement can be completed alone or with other players. Only one person has to get a platinum score in a level for it to count for that level, so multiple players increase your chances. Platinum medals are awarded when a player exceeds a certain score on a level; these scores vary among the 42 levels, however.
Unlock the "Oooh... Shiny!" achievement by earning a platinum medal or by playing with someone who earns one in Free Play mode. If attempting "Platinom Nom Nom," this achievement will be unlocked after the first medal. Generally, it is best to play levels on basic difficulty when trying for platinum. Two of the easier game types are "20,000 Leaks" and "River Rush." In "20,000 Leaks," players must stop leaks to raise their score. In "Leaks Ahoy," one of the first levels, you need a score of at least 140 to receive a platinum medal. In "River Rush's," first level -- "Curvy Creek" -- you must guide your raft through obstacles and collect coins. A score of at least 160 is required for a platinum medal.
Unlock "Jump The Shark." To do this a player must make the shark jump in the "Living Statues" section of the game. The shark living statue is accessed by selecting "Show off and Share" from the main menu and then "Living Statues." Select "View" on the shark and then "Record." After the recording begins, you will see yourself inside of the shark's mouth. Jump in the air to make the shark jump as well, unlocking the achievement.