Below is the task to complete in order to unlock the bonus feature "Free Credits". This simply means that the arcade core of the game is removed with the ability to Continue after time runs out an infinite number of times. Consider this an 'Unlimited Lives' cheat. To access this once unlocked simply head to Options in main menu and change Credit value to 'Free'.
Below are the tasks required to unlock two additional bonus lakes within the game to be used in all Play Types except World Monsters and Tournament. Note: Save and Load may be required after achieving the tasks in order for the game to recognise it. To view your catch amount, simply view the details of the memory card block (start the PS2 with no disc but with memory card inserted).
Below are the levels in World Monsters that can be unlocked: