Beneath India’s coastal waters lie remnants of advanced civilisations that thrived millennia ago, their stories preserved in stone and sediment. Among the most compelling is Dwarka, Gujarat’s legendary city linked to Lord Krishna. Since the 1980s, the National Institute of Oceanography (NIO) has uncovered submerged structures, including fortified walls and a 200-meter jetty built from interlocking basalt blocks. Radiocarbon dating of artefacts suggests the city flourished between 1700–1400 BCE, aligning with the post-Harappan eras. Sonar mapping in 2025 revealed a 3-km² grid-planned settlement, corroborating the Mahabharata’s account of Krishna’s kingdom sinking into the sea.

Further south, Poompuhar (Kaveripoompattinam), the Chola dynasty’s ancient port, lies submerged 25 km offshore. Bharathidasan University’s 2020 study identified an 11 km × 2 km harbour complex with Roman and Chinese trade artefacts, dating to 15,000 BCE. The city’s four relocations over 20,000 years—tracked through sediment cores—highlight its battle against rising seas, culminating in a tsunami-induced collapse around 1000 CE.

Mahabalipuram’s “Seven Pagodas” myth gained scientific credence in 2004 when the Indian Ocean tsunami exposed Pallava-era structures offshore. The Archaeological Survey of India (ASI) documented a 50-meter granite wall and 7th-century inscriptions, while shoreline models show 200 meters of erosion since 700 CE. UNESCO-led conservation now employs artificial reefs to protect these submerged temples.

These cities tell a story of India’s maritime ingenuity. Dwarka’s wave-resistant dovetail joints, Poompuhar’s tidal sluice gates, and Mahabalipuram’s granite craftsmanship. Together, they reveal a civilisation that mastered coastal engineering long before modern technology.