Magic in the Water (1995)

Dr. Jack Black is a sour, tough-talking Seattle talk-show psychiatrist. Divorced and indifferent to his children, Ashley and Josh, he is shamed by his ex-wife into taking his kids on a vacation to Glenorky, a Canadian resort community. The lake there is rumored to contain its own elusive Loch Ness-style monster. Nobody, however, is having a good time until Jack is knocked on the head, suddenly transforming his personality into a loving, caring father. But he also becomes part of a group of men who feel that the gentle spirit of the mythical lake monster, Orky, has inhabited them.