The plot of Dark Tide is not good. Character development is overacted to the point of parody while also completely underdeveloped. None of us care about any single one of these Characters, or their relationships. Halle Berry works with what she's been given, but she is miscast in this movie and she's about as good of an actor as Kristen Stewart. Sure, she is beautiful, but her acting has never been believable or diverse in anything I've ever seen her in. She's very much one flavor only, and I feel she only ever puts in "just" what's required of her and nothing more. Zero charisma.
All that said, this plot, the story, the characters, the conflicts and situations, the decisions, the choices, predicaments, dynamics of characters and their relationships, the proposals and screenplay are NOT believable. At all. Half of the movie is unnecessary entirely. We don't need, or care about, the arguments between a husband and wife, exes, a greedy and selfish father and son, and we don't, or even care to, understand what all of Halle's overacted anger and mood swings are about. There are WAY too many conflicts, one on top of the other, and a snowball of ridiculously dumb decisions.
But, when it comes to the sharks, that is all very believable. They are not dangerous, but when you tease them and provoke them, they tease back... it's worth a watch. Once.