Go to the beach, ocean, or Ginger Island ocean
Fish during Summer
Fish between 12:00 PM and 4:00 PM
Use a rod and bait if you want
Cast into ocean water
Catch the pufferfish when it appears
Check the Traveling Cart if you miss the season
Check Krobus on Wednesdays if available through special stock
Use a Magic Bait if you want to catch it outside normal conditions