The Church of St. Mary on the Sea is located in the old village of Campomarino and dates back to the 12th-13th century, but it was deeply renovated during the 16th century, with a new architectural style and transforming its interior into a single space.
The church preserves few hints of its ancient romanic architecture, such as the external walls, a walled up door, windows with Gotic arch and two apses. The current structure is made of stone, with a series of hanging bows put on side brackets and pilasters. Inside, after restoration, it is possible to admire the apses and the bases of pillars and columns belonging to previous building.
The two fragments, carved in inlaid polychrome marble and located near the greater altar and the altar of the right sidewall, were certainly made between 1750-1774, as like as a walled font made by a Molise craftsman, carved in stone. Another beautiful element is the engraved and painted wooden pulpit. On the right sidewall there are the statue of St. Antony of Padua, made of painted paper-mache, and an engraved, painted and silvery wooden torso of St. Christina, both dating back to the 19th century. Several sacred furnishings and ecclesiastical ornaments from the 18th and 19th century are preserved in the church and its sacristy.
The rectangular crypt with three apses has arches made of smooth big blocks and small columns engraved with vegetable patterns, and shows several frescoes. One of these represents St. Nicholas with a bishop dress and the titration near his head, together with an mounted Saint armed with a spear, whose identification is difficult. It is not easy to understand whether he is St. George or St. Demetrius. Another fresco shows a man knocked down and mashed by a horse, an uncertain representation of a Turkish raid on the Adriatic coast. Finally, on the lateral and background walls there are stone-carved capitals from the 12th century, made by Molise stonecutters.