The igapó — flooded forest — is the signature habitat in high water, roughly May to August, when canoes paddle among the crowns of drowned trees and you look down through clear black water at submerged trunks. Wildlife concentrates in the canopy: monkeys, sloths and birds.

The channels between islands hold Amazon river dolphins — both the pink boto and the smaller grey tucuxi — which surface regularly and are among the most reliable sightings of any trip.

The beaches exposed in low water, roughly September to February, are where river turtles nest and where night spotting for caiman along the sandbanks is easiest. Trails through the forest also become walkable, adding tarantulas, poison frogs and the possibility of terrestrial mammals.

The night boat is the reliable caiman activity, along with fishing bats, potoos and the extraordinary chorus of frogs and insects that defines a blackwater night.

The forest generally holds squirrel and howler monkeys, sloths, and a strong bird list including hoatzin, several macaw species and the tiny endemics of Rio Negro campina scrub.

Practicalities

Anavilhanas is reached from Novo Airão, around two hours by road from Manaus, or by boat from the city. Lodges range from simple community-run operations to a well-known ecolodge on the riverbank.

The Meeting of the Waters near Manaus, where the black Rio Negro runs alongside the brown Solimões without mixing for kilometres, is on the way and worth the stop. Choose your season deliberately: high water and low water are genuinely different trips, and no operator can give you both.