How do our ancient texts written by Valmiki and Tulsidas mention the stone bridge to Lanka without the writers ever having visited the site? How were flying machines mentioned when aeroplanes were thousands of years away? Every writer is only a mirror of his own times, which goes to prove that these things did exist in their times. Whether it was Ram or someone else who got the bridge built is beside the point but the fact remains that a bridge was indeed built between Lanka and the southern tip of India.
Sethusamudram project which will facilitate navigation in the area has nothing to do with these facts or beliefs. Development can be carried out by accommodating the Hindu belief as far as possible.