I think that the movie begins at yacht party, something goes wrong, the yacht is shipwrecked, but fortunately they are close to the shore, they swim to a seemingly deserted island.
Those people from the yacht start organizing their lives on the island, but some kind of pirates show up from the see. They weren't pirates like in Pirates of the Caribbean, but something like a gang with modern weapons, on a modern yacht. I don't exactly remember what happened, the people lived, but really got scared, so they later start building some kinds of traps over the island, because those pirates always come back.
All I can remember is that later a baby is born in the island, which means they stayed they for a long time.
And I remember that somewhere close to the end there was a scene in a cave, where they hid the baby from pirates, and also set some traps there, so that's how they defeated the pirates.
I hope this is enough, I remember just these things, all I know is that I really liked the movie, it was a great thriller, some action and so on.
Thanks in advance!