The Sunderban outlines the gigantic fertile delta that is the meeting point of the three mighty rivers mentioned earlier. The smaller Vidya Malta river, divides the region into the western Namkhana Range and the eastern Bashirhat Range. The swamps lie at the feet of the Himalayas in the north, the Rajmahal hills in the west and the Meghalaya plateau and Chittagong hills in the east. The notified forest area, supports dense mangrove forests, several rivers, creeks and estuaries but most of the area is inaccessible swamps. Sajnekhali, Lothian Island and Halliday Island form the three most important island areas of the reserve. The Sunderban comprises the Chhotahardi, Mayadwip, Chamta, Matla, Goshaba, Gona and Baghmara forests. The soil texture resembles sticky clay and flooding is a daily feature when two-thirds of the land gets submerged. Water logging is an obvious fall-out of the hydrology of the area.

Watchtowers at strategic locations enable a greater likelihood of wildlife sightings. There are watchtowers at Sajnekhali, Sudhanyakhali, (khali means canal or creek and almost all names end so) Netidhopani and Haldi among other places. The first three are key Project Tiger Islands.

A heron sanctuary near Sajnekhali is a gorgeous spot, ideally visited between July and September. Herons, egrets and other waders may be seen here. Egrets are more common around Sajnekhali while the White Bellied Sea eagle, Black-capped Kingfisher and the tern, whimbrell and curlew are more likely to be seen at Lothian Island.

Fraserganj is a busy fishing village, which also attracts a sizeable migratory bird population. Mayadwip offers sanctuary to the endangered Olive Ridley turtle.

The area is unique given the salinity of its lands. While creeks and streams invigorate the area with freshwater, tides sweep the area at least twice a day. The tides rise inwards as much as 75 m and their effect is seen on the thriving mangroves. They have a beneficial effect on ground water salinity since they reduce the salt content through chemical exchange and capillary mechanisms. It is estimated that 26 of the 50 mangrove species known worldwide can be found in the tropical forests of the Sunderbans.

The highly saline Namkhana areas that lie west of the Raimangal-Kalindi River, support less vegetation as compared to the Bashirhat region. To a large extent, the kind of vegetation is determined by the firmness and consistency of the soils and climatic conditions. Almost all trees except the Sonneratia Apetala growing in the eastern stretches, are restricted to less than three to four metres in height. It is the density of the forests that make them impenetrable. Pneumatophores or aerial roots are a biological adaptation for survival in this region typical of tidal areas. Halophytic shrubs take root and grow on dry soils.

Wild dates and palm grow on the more elevated land. Golpata, that resembles a coconut tree without its stem grows here. Orzea Coarctata is the primary grass species found in the area.