Beacon Promontory (5E)

From publisher blurb:

Beacon Promontory arose from the watery grave of Beacon Cove after a ferocious storm submerged the village. The handful of doughty survivors 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 or were killed in the storm, but they feel they have a duty to seafarers who become stranded along the remote stretch of coast. However, the truly insane person may be the lighthouse keeper who believes the deluge that destroyed Beacon Cove was a precursor to an invasion from beneath the waves.