Deep Current

Structural lore — how ships reach the deep sea (and ultimately Fish-Man Island) by riding ocean currents.

What we know

• Ch. 604 p. 12 — The surface current a coated ship rides is distinct from a hidden deep current that flows “all around the world uninterrupted,” surfacing and submerging “like a giant dragon” (Brook). Legend attaches: ride it to the bottom and “you wouldn’t see the light of day again for 2,000 years” — monsters, curses, lost souls (p.13).
• Ch. 604 pp. 12-14 — A downwelling current / plume connects the surface current to the deep current. It forms where water becomes cold, heavy and salty and sinks (Franky’s bath analogy: hot at the top, cold at the bottom). Conditions: severely cold winter islands, and sea-ice formation raising salinity.
• Ch. 604 pp. 15-17 — The plume manifests as a literal underwater waterfall, thousands of feet in diameter, plunging into pitch-black depths; the Sunny rides it down toward Fish-Man Island.
• Ch. 604 pp. 10, 18-19 — Predators (the Kraken) and “underwater travelers” who tame sea beasts to tow ships exploit this route.

Chronology / structure

The deep-sea route to Fish-Man Island: surface current → downwelling plume (cold/salty winter-island water sinks) → the deep current → the seafloor at the Red Line midpoint.

Open questions about this topic

• (None tracked yet — the deep-sea geography is established lore, not an open mystery.)

Cross-links

• Locations: Fish-Man Island, Red Line.
• Ships: Thousand Sunny (rides the plume @0604).
• Sibling current-lore: Reverse Mountain Current System.
• Creatures: Surume (the Kraken guarding the route).