CONTAINS GLUB GLUB GLUB SPOILERS
Remember Open Water? Well, this is essentially the same film. Or Adrift, which in some places was actually known as Open Water 2 despite having nothing to with Open Water apart from having people stuck floating in the middle of the ocean. To all intents and purposes The Reef is exactly the same story, and rather blows its "Based On True Events" caption at the start by including the "all characters and incidents are fictitious" disclaimer at the end.
Whether the events of the Australian film The Reef are true in any meaningful sense or not, they do not, unfortunately, make for gripping drama. Two couples (one estranged) get together on an ocean yacht but after a few days they rip the hull open on a coral reef, the boat capsises and they're all stranded on the fast-sinking wreck, twelve miles from land and with no food or water. With the one crewman opting to stay on the upturned hull with the distress beacon, the others decide to swim through shark territory for the nearest island. How many of the four will make it?
It's very repetetive: a shout of "What was that?!?!", a glimpse of something that might be a fin, a long underwater shot into the murk and the answer "I dunno"..... over and over again. Sometimes there's a shark visible, sometimes there isn't. And when it is, the shark attacks are very quick. Nor are we given that much reason to care about these people. It's acceptably enough done but overall, as with Open Water and Adrift, it's just not interesting enough to hold the attention.