Abyss? Abysmal is closer to the mark. This survival horror from Australia – pitting man against killer croc – swims in the shallow end of scares. It creates the merest ripples of fear, despite contriving a nightmarish escape-proof predicament for its victims: four friends on a caving trip who become trapped on the banks of an underground lake as it fills with water, a croc the size of a minibus snapping at their feet.