"For boats, it is not one size fits all", says Bhattacharyya. The design, shape and the material used is determined by the river that the boat will have to sail on and the purpose. A boat that plies along the slow moving rivers of south Bengal will not be the same as the boats that have to negotiate the swift rivers of the hilly north. A luxury boat will not be the same as a local ferry. A passenger boat will not be the same as a cargo boat. And both will be different from a fishing boat. Even if the purpose is the same, the boats may differ. For example, both dholai and khorokishti are cargo boats. But dholai, mostly seen in the Sunderban region, initially used to carry wood, now also carry bricks, tiles, etc. It has a deep v-shaped hull. But the khorokishti, which carries hay, has a wide flat bottom. Paukhia, another type of cargo boat, is meant to navigate shallow creeks. Maintaining the centre of gravity and buoyancy are two of the many things that a boat-maker has to keep in mind.