Beacon Promontory (Pathfinder)

From publisher blurb:

Beacon Promontory arose from the watery grave of Beacon Cove after a ferocious storm submerged the village. The handful of doughty northerners rebuilt their homes around Beacon Lighthouse, which lights the way for passing ships, many of which used to make the former village a port of call. Many consider the holdouts insane for staying, considering over half their neighbours left, but they feel they have a duty to seafarers who become stranded along the reshaped coastline. However, the truly insane person may be the lighthouse keeper who believes the deluge was a precursor to an invasion from beneath the waves.