Hatchan's Sea-Floor Stroll

Hatchan's Sea-Floor Stroll (はっちゃんの海底散歩 Hacchan no Kaitei Sanpo, Hachi's Walk on the Seafloor in the English manga) was the 4th Mini-Series created as side stories on the title pages of each One Piece chapter.

Length
ch. 182–228 (40 installments)

Short Summary
Having escaped from the marine ship where he is held, Hatchan returns to beneath the sea and inadvertently helps a panda-shark. This sets off a series of trades and adventures, culminating in the discovery of a new friend, Keimi the mermaid, and the fulfillment of his dream - a takoyaki stand.

Chapter Titles

 * 1) Jailbreak (chapter 182)
 * 2) Time to go home (chapter 183)
 * 3) Hatchan saves a Panda Shark (chapter 184)
 * 4) Hatchan gets meat as thanks (chapter 185)
 * 5) Hatchan meets a hungry man (chapter 187)
 * 6) Hatchan gets a ring as thanks (chapter 188)
 * 7) The Goldfish Princess who lost her ring (chapter 189)
 * 8) Hatchan gets a golden trident in thanks (chapter 190)
 * 9) The giant Seaboar being chased by a Sea Monster (chapter 191)
 * 10) Hatchan saves the Seaboar (chapter 192)
 * 11) From inside the Seaboar's mouth comes... (chapter 193)
 * 12) Keimi the Mermaid and Pappug the Starfish (chapter 195)
 * 13) The shadow that approaches Hatchi after he saved them from almost being eaten by another fish after being eating by a fish (chapter 196)
 * 14) Introducing the Macro Fishman Pirates (chapter 197)
 * 15) Reunion with the dear old Chums (chapter 199)
 * 16) Surprise Keimi!! Deal to the Fishmen for Takoyaki map (chapter 200)
 * 17) Search for the legendary Gekiuma Takoyaki recipe (chapter 202)
 * 18) Prepose one more time to the darling Octopako (chapter 203)
 * 19) At the maps end lies the great Octopus Mash (chapter 204)
 * 20) Hatchi's wrath at being fooled!! (chapter 205)
 * 21) Where are they? (chapter 206)
 * 22) Mermaid selling Maros (chapter 207)
 * 23) Octopus Punch! (chapter 208)
 * 24) You can't trick me! (chapter 209)
 * 25) The best cooking sauce found (chapter 210)
 * 26) Both treasures acquired, no one can stop me! (chapter 211)
 * 27) Octopako was out at the moment (chapter 212)
 * 28) Too bad! The headband catfish village crushed by a sinking ship (chapter 214)
 * 29) Hatchi comes to the starving Catfish village (chapter 215)
 * 30) Hatchi's escape! (chapter 216)
 * 31) Save the catfish village! Hatchi turns the treasure into ingredients!  (chapter 217)
 * 32) We're now open, Hatchi's Takoyaki stand (chapter 218)
 * 33) The catfish village is now saved, now one last batch to my marriage proposal (chapter 219)
 * 34) Octopako is attracted by the smell of the sauce (chapter 220)
 * 35) The catfish elder who came last (chapter 222)
 * 36) Octopako's punch and elder's smile (chapter 223)
 * 37) Hatchi and the sunset (chapter 224)
 * 38) Under the warmth of the setting sun, remembering the dream of a Takoyaki stand (chapter 225)
 * 39) The catfish village shows its thanks (chapter 227)
 * 40) Grand opening of Takoyaki '8' (chapter 228)

Trivia
It is asked in SBS if Hatchan was a champion of eating Takoyaki(octopus fritters) because of his attack.