Solution:

Adam’s Bridge also known as Rama’s Bridge or Rama Setu is a chain of limestone shoals, between Pamban Island, also known as Rameswaram Island, off the south-eastern coast of Tamil Nadu, India, and Mannar Island, off the north-western coast of Sri Lanka. Geological evidence suggests that this bridge is a former land connection between India and Sri Lanka.

The bridge is 50 km (30 mi) long and separates the Gulf of Mannar (south-west) from the Palk Strait (northeast). Some of the sandbanks are dry and the sea in the area is very shallow, being only 1 to 10 meters (3 to 30 ft) deep in places, which hinders navigation. It was reportedly passable on foot up to the 15th century until storms deepened the channel: temple records seem to say that Adam’s Bridge was completely above sea level until it broke in a cyclone in 1480.