"These ships are a lifeline for the people," 18-year-old Washington told AFP, travelling between two tiny green specks in the 800-kilometre-long (500-mile) Indian Ocean chain, from Chowra to the slightly larger Car Nicobar."If I had missed this one, I'd have to wait for the next one for a few days," Washington said, after clambering onboard the government-run MV Kalighat, an 85 metre-long (278 foot) cargo and passenger vessel.

India's strategic archipelago © Nicholas SHEARMAN / AFP

Washington's journey lasted about five hours on the ferry service that takes up to 50 hours from end to end.Running from the archipelago's capital Sri Vijayapuram in the north to the southern tip of Campbell Bay, the ferry serves as both a passenger and cargo ship linking the 836-island archipelago. At each stop, passengers like Washington or others laden with sacks of coconuts or pineapples for the market get on and off.At bigger ports, a few cargo containers are loaded or unloaded.Many islands like Chowra -- a three-kilometre-long (two-mile) forest speck in a vast blue sea -- lack deep-water jetties.So passengers must reach ocean-going ferries by smaller tenders.

Workers load goods onto the MV Kalighat vessel at Katchal in India's Andaman and Nicobar Islands © R. Satish BABU / AFP