I liked this movie, but I would change one thing:

This assumes that you have seen the movie, therefore, spoilers.

-I liked the tone of the movie. It's some sort of documentary, a la Discovery Channel.
-I liked the ending; no one comes back but they manage to send to earth info proving the discovery of life on Europa.

However I feel that the payoff is delivered too soon when they find living algae on the surface. That, on itself, is proving that there is life on other planets, so having the squid in the end doesn't add much to it.

Anyways, I'd have loved to see a bigger discovery in the end. Rosa sinks with the ship, but as she descends underwater she should be able to see traces of civilization. Buildings, roads, intelligent behaviour. Perhaps more creatures trying to aid her. Of course that would bring the movie more to The Abyss territory, but probably that would have made more people feel content with the ending.