For a show which is all about an alien invasion, it was a very damp squid, which is more what the aliens turned out to be. There was lots of mystery, lots of intrigue about the lights in the water, but it just dragged on and on, nothing ever happened and after 12-15 episodes, it wasn't worth the bother. Look at Lost's example, over 2 seasons, more and more was revealed which posed more and more questions. In invasion there is just more and more questions about nothing. After 12 episodes there was little threat from any aliens, and there was still no sign of them. 'Invasion' is a bit of an exaggeration, more like 'we're coming to your planet but we won't do much, fiddle with a few people, lurk around in the water a bit on the whole you wont notice us' but probably a bit snappier so it fits in the TV listings.