The final immersion day of Ganesh Chaturthi in Mumbai, when tens of thousands of Ganesha images, from small home idols to towering pandal centrepieces requiring cranes to move, are carried in procession to the sea, most famously converging on Girgaon Chowpatty beach, has grown into one of the largest coordinated public logistics operations the city undertakes each year, requiring extensive traffic diversions, thousands of police and volunteer personnel, dedicated immersion points along the coastline, and lifeguard and rescue teams stationed specifically because the crowds and the underwater debris from earlier immersions create genuine safety hazards for participants wading into the sea.
Municipal authorities in Mumbai and other Maharashtra cities now plan for the immersion days months in advance, coordinating with the mandals that run the largest public pandals on timing and routes to prevent the kind of dangerous overcrowding that has occurred in past years, so that a religious act of returning a clay deity to the elements has become, at the scale a modern megacity now celebrates it, as much a matter of civic crowd-safety engineering as of devotional practice.
The festival has also taken root well beyond India among the Hindu diaspora, with public Ganesh Chaturthi processions and pandals now organised annually in cities including London, New York and various centres in the Caribbean and Southeast Asia with large Indian-origin populations, generally on a much smaller scale than Mumbai's but following the same basic pattern of installation, daily worship and a final immersion, adapted to local rivers, lakes or the sea where one is available.