On shore, staff try to instill a regime of dental hygiene, getting the children to sit for long minutes with fluoride paste on their teeth, and using a toothbrush.
For the older members of the village, like Pedro Silva, 67, it's too late.
"I'm going to get a consulting note to see about the last tooth I have in my mouth," he says with a cackle that frames the solitary tooth in a cavern of black.
Some of the problems are more serious. One middle-aged man looks around in befuddlement, blood coagulating on his forehead from a bathroom fall that, he finds out, also broke his shoulder.
Sexually transmitted diseases are also rife, as are teenage pregnancies.
On a past trip to another village, the ship's medics discovered one sickly girl was suffering from leukemia.
While the ship sets about treating the residents, some of the staff hand out simplified Bibles, to be colored in or taken apart as jigsaw puzzles, to the scores of children.
These are gifts from the charity that owns the vessel: the Brazilian Bible Society, the world's biggest publisher of the Christian book which sees spiritual health as much in need of help as physical wellbeing.
On both counts, the Amazon is a fertile region for the hospital ship's services.
The impoverished communities which live in isolation, relying on the rivers as the only practicable pathways through the jungle, are grateful for the medical aid they would never otherwise see, and the literacy boost provided by the Bibles.
Acyr Degerone Junior, in charge of the ship's program, says the idea is "to treat people who don't have medical access, who can't get to a town, who don't have that option."
He won't be drawn, though, on whether the fact that the ship fulfils a need means that public authorities are not doing enough to care for the communities.
"The program is concerned more with giving an option to these people, than us thinking about whether we see an absence of public services in these areas," he said.
After a two-day stop on Mocajuba Island, the hospital ship slips its moorings and heads out into the river, back to Belem for restocking and to change its team of volunteers.
It will be a brief return to civilization before returning to the jungle waterways, on yet another of its thrice-weekly trips.
Source-AFP
THK