The plot: Sisters Lisa (Mandy Moore) and Kate (Claire Holt),
while on holiday in Mexico, are invited by two locals to go shark cage diving.
They agree and head down in the cage, but they soon find themselves in trouble
when the winch holding up the cage breaks, sending them plunging 47 metres
underwater. With only a limited supply of oxygen and many sharks swimming
nearby, Lisa and Kate have to find a way to contact their boat and get back to
the surface.
