There were long stretches of smooth-worn rock running for miles , exactly fitted to make seal-nurseries , and there were play-grounds of hard sand sloping inland behind them , and there were rollers for seals to dance in , and long grass to roll in , and sand dunes to climb up and down , and , best of all , Kotick knew by the feel of the water , which never deceives a true sea catch , that no men had ever come there .