The Water Horse: Legend of the Deep

Two children discover an egg on a beach in Scotland which hatches into a "water horse" that grows to be the Loch Ness Monster. (Source)

A lonely young boy vows to protect the rapidly growing hatchling that emerges from a mysterious egg found on the shores of a Scottish loch in My Dog Skip and Tuck Everlasting director Jay Russell's screen adaptation of writer Dick King-Smith's popular children's novel. Angus MacMorrow (Alex Etel) has made a most unusual discovery, and he's about to find out just how one innocent boy's greatest fantasy can also be a frightened adult population's greatest threat. Unable to identify the egg that he found while walking the sandy shores, Angus is even more perplexed about the discovery and the creature that emerges resembles what comes to be known as a Water Horse, which Angus names Crusoe. As the bizarre new life form begins to grow at an alarming rate, it soon becomes obvious that Angus will not be able to keep it a secret for very long, and the young boy will have to do some seriously quick thinking if he is to keep his new friend safe. - Jason Buchanan, All Movie Guide (Source)