Sonic lure:
Successfully complete all five professional tournaments in original mode.

Female character:
Press A + B at the arcade mode level selection screen.

Alternate clothes and boat color:
Reach the final tournament in original mode for new clothes and boat color.

Secret practice levels:
Successfully complete the game once in arcade mode. Three new levels will be unlocked under practice mode. Successfully complete Lake Paradise in original mode to unlock the Palace level in practice mode. Successfully complete Lake Crystal in original mode to unlock the Falls level in practice mode.

Hint: Keeping low line tension:
After your tension gets up very high in red, sweep the Analog-stick in clockwise full circles. If done correctly, the tension will go down extremely low, allowing you to reel in big fish. Keep sweeping the Analog-stick to cause the fish to become tired.

When you have a large fish on your line, or a fish that has a lot of energy, tap your Reel button at a slow rate. While doing this, it gives the line just enough time to keep the line easy, and enough time to hold on to the fish without it snapping your line. This should work for any fish of any size, no matter what type of challenge. If the line gets very tense, release it and let it go into the yellow zone for about a second. Then, keep tapping it at a slow rate.

Hint: Knock armored head off in Palace level:
Use the Deep Crank or Sonic bait and cast it to the left of the palace's front door. Reel it all the way in until it sinks to the point where it is directly behind that armored body's head. Keep reeling it in, and if your bait hits the back of the armored head, it will fall off.