Monster from Out of Time - Frank Belknap Long - Bog

IT CAME FROM THE SEA-
-huge, hairy, glowing, terrifying. On the beach, people gathered to stare-from a distance-at a creature unlike any they had ever seen.
David, a young scientist, and his girlfriend, Joan, were among them. But David was not content with a distant look. At sundown, when the crowd had gone, David and Joan returned.
And that's when it happened.
A blinding light was all they remembered. Suddenly David and Joan were plunged through time into a world of towering glaciers and prehistoric beings-into an adventure of cataclysmic terror from which there seemed no escape!