The roots of the Sensa Feast-day, on the occasion of Ascension Day (in Venetian dialect Sensa) lie in the history of Venice and more specifically in two episodes: the conquest of Dalmatia by the Venetians and when Doge Ziani acted as mediator between Pope Alexander III and Emperor Frederick Barbarossa (Peace of Venice, 1177).
The Marriage of the sea ceremony took place on the occasion of this feast. The Doge of the Serenissima used this rite to demonstrate the Republic’s dominion in the Adratic. The doge and his entourage embarked on the Bucintoro. On reaching the mouth of San Nicolò port, the Doge threw a gold ring into the sea.
The symbolism of the mystic marriage to the sea is still evident and is certainly still valid today. The Mayor of Venice, civic dignitaries and religious and military representatives leave Saint Mark’s Square and sail to the Port of S. Nicolò where the ritual ring throwing takes place.
From “DeTourism”