Canaletto (Giovanni Antonio Canal). Bucentaur’s Return to the Pier by the Palazzo Ducale. Circa 1730.

In Canaletto’s painting Bucentaur’s Return to the Pier by the Palazzo Ducale, the scene depicts a ritual significant to Venice—the marriage of the leader of the Republic to the sea, known as "Marriage to the Sea" (ital. Sposalizio del Mare), held during the Feast of the Ascension, known as La Sensa. This tradition originated around the year 1000, when Doge Pietro II Orseolo of the Venetian Republic achieved a major naval victory in Dalmatia. In commemoration of this event, the solemn ceremony of the "Marriage to the Sea" became an annual observance. Initially, it consisted of a simple prayer to the sea but evolved in the 12th century.

In 1177, Pope Alexander III visited Venice and presented the Doge with a number of symbolic objects in gratitude for his assistance in resisting the Holy Roman Emperor. During the "Marriage to the Sea" ceremony, the Pope removed a ring—which he himself had given to the Doge—from the latter’s finger, recited a prayer, and instructed the Doge to cast the ring into the sea "as a sign of true and eternal dominion" over the waters of the Adriatic. At that point, the ancient ritual took its final form. The ceremony was held annually until the fall of the Venetian Republic in the late 18th century.

Over time, the "marriage to the sea" ritual evolved into a meticulously staged spectacle. The symbolic dimension of the historical event took material form, as Venetian rulers compelled to affirm their dominion over the Adriatic in the absence of any formal legal documentation substantiating their claims. The ceremony thus included a grand procession, with participants carrying gifts said to have been bestowed upon the Doge by the Pope. Among these were a white candle (symbolizing purity and religious orthodoxy), a sword (representing the defense of the faith), as well as a lead seal, an umbrella, trumpets, and banners.

The marriage rite itself traditionally began with a prayer recited by the Catholic Patriarch of Venice aboard the Bucintoro. Then, at the mouth of the lagoon—where the Venetian Gulf meets the Adriatic Sea—he would pour a vial of holy water into the sea, while the Doge, in turn, cast his golden ring overboard, proclaiming: “Desponsamus te, mare” (Latin for “We espouse thee, O Sea”).

The choice of the "marriage" ritual was deliberate. In Europe until the 17th century, the state was often likened to a family, and rulers to fathers and husbands. Venetian law codified a husband’s authority over his wife in accordance with Christian tradition, which positioned the husband as the head of the household and protector of its members. By transposing this legal concept of marriage onto maritime law, the Venetians established an unequal ritual partnership—one in which they, as the "head," exercised sovereign authority over Venice’s subordinate maritime territories while pledging to protect them.

When the Catholic Patriarch of Venice recited prayers over the sea and sprinkled both the waters and the Doge with holy water, he was effectively blessing this metaphorical union between the Doge and the Sea. The ritual thus sanctified Venice’s claim to the Adriatic, reinforcing its commercial and political hegemony over these waters.

The "Marriage to the Sea" ritual also served to solidify international recognition of Venice’s claims over the Adriatic. This was achieved through the presence of foreign ambassadors at the ceremony, which signaled their states’ tacit acceptance of Venetian dominion in the region.

In Venice, symbols and allegories held particular significance - including for political purposes. An observant viewer would note the figure of Justitia on the Bucintoro's prow, embodying divine law and natural order. The presence of  Themis on the galley's bow emphasized that the goddess, as witness, was meant to validate the ritual's legal authority.

Given that Venice was renowned for its complex governance, extensive trade networks, and need for a fair legal system to mediate disputes among its diverse population,  Themis particularly is represented the Republic's legal and moral ideals. Moreover, the goddess's image symbolized Venice's heritage and connection to classical antiquity, demonstrating that the Republic stood equal among other major political centers.

The image of  Themis appears in various artistic elements, sometimes depicted in public buildings and triumphal monuments. Notably, in the early 15th century, a statue of the goddess was installed on the roof of the Doge's Palace, flanked by two lions symbolizing Saint Mark the Evangelist - Venice's patron saint.

In Venetian iconography, Themis was occasionally portrayed holding an umbrella - one of the gifts from Pope Alexander III to the Doge and a symbol of sovereignty. The privilege of using the umbrella as an emblem of secular power was reserved exclusively for Roman pontiffs and Holy Roman Emperors. This bestowal carried profound significance, as it signified Venice's autonomy through recognition of the Doge's authority as equal to that of both Pope and Emperor.

The umbrella-bearing Themis became the very embodiment of the Republic. Through this multifaceted symbolism, wealthy and magnificent Venice laid claim to divine wisdom and justice in establishing its civic order.

In Bucentaur’s Return to the Pier by the Palazzo Ducale, as in other works by Canaletto, the depicted events are rendered with meticulous attention to detail. The artist achieved this remarkable precision through innovative use of the camera obscura. This optical device - a box with a small aperture through which light passes, projecting an inverted image of the scene onto the opposite surface - allowed Canaletto to capture separate elements of the landscape.