The Uninvited (1997)

Photographer Steve Blake witnesses a horrific car crash, in which James Wilson, head of British Nuclear Power, is burned to a crisp. He is stunned the next day when he sees Wilson alive and well, the inquest reveals unanswered oddities, and the detective heading the investigation, John Ferguson, is eager to close the case. When he investigates similar victimless deaths, he learns that Wilson was one of 200 survivors, several years earlier, when coastal village, Sweet Hope, collapsed into the sea, the entire populace saved by 2 policemen (Ferguson and Chief Supt Gates) - and they all seem to have moved up in their various fields suspiciously quickly since. When Gates's wife suggests he could have been replaced by an alien after the tragedy, Blake ventures underwater, where he's horrified to find the skeletons of all of Sweet Hope's inhabitants ! So, who are the survivors...?