If a ship has to go from Chennai to Kochi, it has to go around Sri Lanka rather than crossing through the Palk Strait. Why?

Ships traveling from Chennai to Kochi must circumnavigate Sri Lanka because the Palk Strait is too shallow for large vessels to navigate. The strait is characterized by a 30 km stretch of discontinuous sandbars and limestone shoals known as Adam's Bridge or Ram Sethu [1]. These geological formations create a shallow barrier between the Palk Bay and the Gulf of Mannar, with water depths in some areas being as little as 1 to 3 meters. Consequently, large ships with significant tonnage cannot pass through this region and must take a longer route around the southern tip of Sri Lanka. The proposed Sethusamudram Shipping Canal Project aims to address this by dredging a deep-water channel through these shoals to create a navigable passage, which would significantly reduce the travel distance between India's eastern and western coasts [1].

Sources

1. [1] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 12: Transport, Communications and Trade > Adam's Bridge (Ram Sethu) > p. 25