Chapter 604: Into the Depths

The Thousand Sunny keeps sinking through the ocean, and the crew notices that sunlight barely reaches them now. Franky places their depth at roughly a thousand meters, past the levels he calls the Euphotic and Disphotic Zones. Robin remarks on the strange quiet, comparing it to flight rather than a submarine, while a pod of blue whales drifts by and stirs both Brook and Luffy. Hidden behind the ship, a vessel belonging to the Caribou Pirates closes in, dragged forward by a shadowy sea creature as Caribou rallies his crew to seize the Straw Hats' heads.

When the rival ship pulls alongside, Nami recognizes the beast hauling it as Momoo, the sea cow once kept by the Arlong Pirates. Terrified at the sight of Luffy and Sanji, Momoo bolts the other direction and tows the entire crew away, leaving only Caribou stranded on the Sunny's deck. Caught alone, Caribou abandons his bravado, begs for mercy, and tries to pass himself off as a mistreated victim. Chopper falls for it; Usopp does not. After Sanji kicks the leering stowaway away from Nami, the crew binds him and presses on.

Brook, Franky, and Nami then walk the others through the science of the deep, explaining how surface and deep currents interlink across the whole world like a single endless dragon, and why riding a descending current is the only safe route down. Their lecture eventually bores Luffy, Zoro, Usopp, and Chopper into silently sipping tea. The ship finally reaches an enormous undersea waterfall Nami calls a Downward Plume. At its base waits a kraken devouring lost vessels, and Luffy promptly announces he intends to tame it as a pet.

Momoo returns, having seemingly been taken prisoner by Caribou's crew somewhere around Sabaody, and flees in fear upon seeing Luffy and Sanji. Caribou is separated from his crew, stranded aboard the Sunny, caught, and tied up after fooling only Chopper. The mechanics of deep sea currents are laid out in detail, and the crew arrives at a vast Downward Plume that descends toward a kraken. Luffy declares he will make the giant creature his pet.

The color spread references the Grimm fairy tale Town Musicians of Bremen. Sanji requires another transfusion because his nosebleeds keep draining him, and a rehabilitation method is floated to manage his condition. Chopper spoils one of Brook's skinless-body jokes before he can land it. Although Caribou is a Logia user, he deliberately lets Franky grab him and Sanji kick him, concealing his powers while he waits for an opening. Luffy's vow to tame the kraken marks the second creature he has tried to claim, following the Cerberus he met earlier on Thriller Bark.