is the undersea way built in \ramayana proved by science?

Answer 1

Sort of.
Satellite images depict ADAMS brigde between India and Sri lanka as the evidence.

Rama's Bridge, also called Nala's Bridge and Adam's Bridge is a chain of limestone shoals, between the islands of Mannar, near northwestern Sri Lanka, and Rameswaram, off the southeastern coast of India. The bridge is 30 miles (48 km) long and separates the Gulf of Mannar (southwest) from the Palk Strait (northeast). Some of the sandbanks are dry and the sea in the area is very shallow, being only 3 ft to 30 ft (1 m to 10 m) deep. This seriously hinders navigation. It was reportedly passable on foot as late as the 15th century until storms deepened the channel. (citation required). A ferry service linking the island and port of Rameswaram in India with Talaimannar in Sri Lanka has been suspended for some time due to the fighting between Sri Lankan government forces and the separatist LTTE; the Pamban Bridge links Rameswaram island with mainland India.