Fisherman's Challenge Cheats (PlayStation 2)

Select All View in Aquarium Mode and press UP, UP, DOWN, DOWN, LEFT, RIGHT, LEFT, RIGHT,
L1, R1. This will place the Wreck of the Robot in your aquarium.

All of the cheats have only one code: 2(up), 2(down), left, right, left, right, L1, R1. 
Its yet another manifestation of the Konami code.  It has different effects depending on
which mode you enter it in.  They are:

  Main Tournament Screen: Increase AI difficulty

  Trolling Motor: Toggle Underwater Mode 

  While retrieving the line: Retrieve line w/o using analog stikc 

  Casting Mode: Hide fish mood lens. 

  Aquarium Mode: Place "Wreck of the Robot" in the aquarium 

  Free Fish Time Mode: Fish at night.

While trolling, press UP, UP, DOWN, DOWN, LEFT, RIGHT, LEFT, RIGHT, L1, R1.

To hide the Fish Mood Lens, press UP, UP, DOWN, DOWN, LEFT, RIGHT, LEFT, RIGHT, L1, R1
while casting.

To increase torunament difficulty, go to the tournament screen and press UP, UP, DOWN,
DOWN, LEFT, RIGHT, LEFT, RIGHT, L1, R1.

To get free fish at night, go to the Free Fish Time  Setting and press UP, UP, DOWN, DOWN,
LEFT, RIGHT, LEFT, RIGHT, L1, R1.

In order to reel your line in without the analog stick, press UP, UP, DOWN, DOWN, LEFT,
RIGHT, LEFT, RIGHT, L1, R1.