The species is amphibious, although primarily terrestrial.
It occurs in freshwater rivers and streams, which generally flood seasonally.
Other water habitats include freshwater springs and permanent freshwater lakes.
Four specific vegetation types occur on one important creek in Suriname: riverbank high forest, floodable mixed marsh and high swamp forest, floodable low marsh forest, and grass islands and floating meadows within open areas of the creek itself.
Duplaix identified two critical factors in habitat selection: food abundance, which appears to positively correlate to shallow water, and low sloping banks with good cover and easy access to preferred water types.
The giant otter seems to choose clear, black waters with rocky or sandy bottoms over silty, saline, and white waters.

Giant otters use areas beside rivers for building dens, campsites, and latrines.
They clear significant amounts of vegetation while building their campsites.
One report suggests maximum areas 28 m (92 ft) long and 15 m (49 ft) wide, well-marked by scent glands, urine, and feces to signal territory.
Carter and Rosas found average areas a third this size.
Giant otters adopt communal latrines beside campsites, and dig dens with a handful of entrances, typically under root systems or fallen trees.
One report found between three and eight campsites, clustered around feeding areas.
In seasonally flooded areas, the giant otter may abandon campsites during the wet season, dispersing to flooded forests in search of prey.
Giant otters may adopt preferred locations perennially, often on high ground.
These can become quite extensive, including "backdoor" exits into forests and swamps, away from the water.
Otters do not visit or mark every site daily, but usually patrol all of them, often by a pair of otters in the morning.

Research generally takes place in the dry season and an understanding of the species' overall habitat use remains partial.
An analysis of dry season range size for three otter groups in Ecuador found areas between 0.45 and 2.79 square kilometres (0.17 and 1.08 sq mi).
Utreras presumed habitat requirements and availability would differ dramatically in the rainy season: estimating range sizes of 1.98 to as much as 19.55 square kilometres (0.76 to 7.55 sq miles) for the groups.
Other researchers suggest approximately 7 square kilometres (2.7 sq mi) and note a strong inverse correlation between sociality and home range size; the highly social giant otter has smaller home range sizes than would be expected for a species of its mass.
Population densities varied with a high of 1.2/km² (3.1/sq mi) reported in Suriname and with a low of 0.154/km² (0.40/sq mi) found in Guyana.
The species is amphibious, although primarily terrestrial. It occurs in freshwater rivers and streams, which generally flood seasonally. Other water habitats include freshwater springs and permanent freshwater lakes. Four specific vegetation types occur on one important creek in Suriname: riverbank high forest, floodable mixed marsh and high swamp forest, floodable low marsh forest, and grass islands and floating meadows within open areas of the creek itself. Duplaix identified two critical factors in habitat selection: food abundance, which appears to positively correlate to shallow water, and low sloping banks with good cover and easy access to preferred water types. The giant otter seems to choose clear, black waters with rocky or sandy bottoms over silty, saline, and white waters. 
Giant otters use areas beside rivers for building dens, campsites, and latrines. They clear significant amounts of vegetation while building their campsites. One report suggests maximum areas 28 m (92 ft) long and 15 m (49 ft) wide, well-marked by scent glands, urine, and feces to signal territory. Carter and Rosas found average areas a third this size. Giant otters adopt communal latrines beside campsites, and dig dens with a handful of entrances, typically under root systems or fallen trees. One report found between three and eight campsites, clustered around feeding areas. In seasonally flooded areas, the giant otter may abandon campsites during the wet season, dispersing to flooded forests in search of prey. Giant otters may adopt preferred locations perennially, often on high ground. These can become quite extensive, including "backdoor" exits into forests and swamps, away from the water. Otters do not visit or mark every site daily, but usually patrol all of them, often by a pair of otters in the morning.
Research generally takes place in the dry season and an understanding of the species' overall habitat use remains partial. An analysis of dry season range size for three otter groups in Ecuador found areas between 0.45 and 2.79 square kilometres (0.17 and 1.08 sq mi). Utreras presumed habitat requirements and availability would differ dramatically in the rainy season: estimating range sizes of 1.98 to as much as 19.55 square kilometres (0.76 to 7.55 sq miles) for the groups. Other researchers suggest approximately 7 square kilometres (2.7 sq mi) and note a strong inverse correlation between sociality and home range size; the highly social giant otter has smaller home range sizes than would be expected for a species of its mass. Population densities varied with a high of 1.2/km² (3.1/sq mi) reported in Suriname and with a low of 0.154/km² (0.40/sq mi) found in Guyana.
Giant otter