This game has plenty of unlockables which are accessed by going to the 'Options' sceen and then 'Cheat Codes' and typing the password in for the effect you want to enable.

Unlock ALL Lakes:
Enter the password 'ALLDLAKES'.

Unlock Extra Money:
Enter the password 'ALLDCASH'.

Slow Boat:
Enter the password 'WHATADRAG'.

Fast Boat:
Enter the password 'HYPERBOAT'.

Bathtub Boat:
Enter the password 'RUBADUBDUB'.

Large Fish:
Enter the password 'MONDOFISH'.

Less Fish:
Enter the password 'WHEREDFISH'.

Easy to Catch Fish:
Enter the password 'SUPERLURE'.

Fish are More Active:
Enter the password 'HAPPYFISH'.

Fisherman have Big Heads:
Enter the password 'HEADADBIGA'.

Remove other Fisherman:
Enter the password 'NOCOMP'.

Catch Al Lindner:
Enter the password 'FISHMAN'.

No Snags when Fishing:
Enter the password 'BAGDSNAGS'.

Unbreakable Line:
Enter the password 'SUPERSTRING'.

Livewell Filled with Large Fish Equaling 55 Lbs:
Enter the password 'GIMMEDFISH'.