Obviously done on a shoestring budget, this is actually quite an interesting little sci-fi/horror mystery. It all centres around the crew of a stranded trawler who come to realise that there is a malevolent beastie that has found it's way into their water supply after their boat strayed into a restricted area. Luckily "Siobhán" (Hermione Corfield) has some scientific skills and plans a way to stop this lethal parasite from killing (rather messily) not just the people on the boat, but anyone they come into contact to. Rather prudently, it does not try to blow us away with fancy special effects. The use of light on the water and some basic microbe imagery conjures enough just enough sense of menace to keep the plot interesting; as do the efforts from a confident Corfield alongside Dag Malmberg and Olwen Fouéré - and Jack Hickey is quite easy on the eye, too! The script is nobody's finest work, and it is a mite too long - but it delivers well enough within it's limitations and kills 90 minutes on the television fine.