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
Kanai barely sleeps again that night. Early in the morning, he gets up and finds that Horen is also awake, watching the water. Kanai asks if there's enough light for Fokir to navigate by, and Horen says with a smile that Fokir just might not want to come back. Horen suggests that Fokir and Piya are in love. Noticing Kanai's surprised reaction, Horen asks if Kanai thinks that someone like Fokir can't fall in love. Horen says that Nirmal was the same way—he was absolutely in love with Kusum but wouldn't admit it.
Horen's insight and questions about Piya and Fokir being in love suggests he's fully aware that outsiders like Kanai and Nirmal don't view the poor people of the tide country as being capable of love. This again shows how the tide country people are at a disadvantage and are thought of as being less than human.
Active
Themes
Horen says he's five or six years older than Kusum. He comforted her when Kusum's father was killed, and he tried his best to protect her. When he took her to Canning to find Kusum's mother, Horen realized she didn't need protecting—she refused his offer to leave his wife and marry her instead. Eight years later, he stumbled onto Morichjhãpi with Nirmal, reconnected with Kusum, and couldn't stay away. Both he and Nirmal used each other as excuses for going to see her. In the end, Kusum chose Horen—she led him to his boat on that last night, and they had sex.
The fact that Kusum chose Horen rather than Nirmal does suggest that Piya and Fokir's relationship likely won't go any further than it already has, given the parallels between the two relationships. Horen's undying love for Kusum, however, also stands in contrast to Nirmal's love of her as a symbol: again, Nirmal's inaction meant he ultimately got nothing.