Gwoemul (Bong Joon-ho, 2006)

As in the early movies of Japan's Godzilla franchise, in The Host the monster that emerges out of a river to terrorise the city populace is created as a result of man-made contamination of the environment. But in this Korean take on nature's revenge on mankind, instead of springing on the counteroffensive, the army sits back and declares the river a biological hazard zone, so it's left to the plucky Park family (the choice of the commonplace name underlines the Little Guy vs. The System-aspect of their quandary) to slay the dragon.
The monster, whilst rendered handsomely in slinky CGI, crops up rather too often and in the open to retain any sense of menace, so that the eye's drawn to dissect which cinematic or mythical forebears it's been put together from, and the family's quest takes no particularly novel turns. Nevertheless, a hovering sense of political frustration at circumstances (the Government and its scientists prove to be either inept, corrupt or insensitive in the crisis, and numerous background news reports refer to Big Brother Uncle Sam's taking charge since South Korea's proved incapable of handling the situation), and some striking inky-toned slow-mo photography help to retain the interest.

5/10