LitCharts assigns a color and icon to each theme in The Hungry Tide, which you can use to track the themes throughout the work.
Language
Man vs. Nature
The Human Cost of Environmental Conservation
Idealism and Theory vs. Practicality and Action
Summary
Analysis
In the afternoon, Kanai tries to talk to Horen about Nirmal's notebook. Horen isn't interested in chatting, but does explain how the notebook got lost in his home and how he found it years later. An hour later, the engine of the Megha dies. Kanai tells a disappointed Piya that Horen plans to float on the currents to a nearby village where someone can fix the engine, and they can be back on their way tomorrow morning. When they get near the muddy shore, one of Horen's relatives and a mechanic row out to the Megha and disappear below deck to work on the engine.
The engine dying and the amount of time it takes to fix it is a very symbolic reminder that humans in the Sundarbans are very much at the mercy of the whims of the natural world, especially when their own manmade tools fail. The presence of one of Horen's relatives on this presumably remote island shows that there's a strong sense of community among the islands.
Active
Themes
As night falls, Piya and Kanai hear the sound of an animal in pain on the shore. Kanai asks Horen about it, and apparently it's the sound of his relative's water buffalo giving birth. Kanai and Piya laugh. Piya decides to go to bed early, and Kanai decides to return to Nirmal's notebook.
Piya and Kanai's concern reinforces their outsider status, a status that will become extremely important soon. They aren't aware of the rhythms of life in the Sundarbans, and that lack of awareness is a detriment for them.