The Water Horse: Legend of the Deep

A Scottish laird is off to World War II and grants the army use of his castle by a loch for his friend, artillery captain Hamilton, to station his garrison -camping, except the officers indoors- to install a battery in case of German submarine attack. Housekeeper .Gracie MacGowan, a presumed war widow, hires handyman Lewis Mowbray. He finds out when her kid son Angus MacMorrow, who found a strange egg loitering on the beach, got it hatching a rare Celtic mythological Nessie-like creature he called Crusoe, which needs bathing, and Lewis recognizes as a water horse, of which only one exists at any time. They try to hide and raise it, but it grows so fast it needs to be released in the loch. Alas, the artillery exercises beginning there put all in danger, forcing them and Crusoe to interact.