Primal (2011)

Synopsis: A group of friends venture into the wilds of Australia to study an ancient rock painting, and comes face to face with an ancient evil when one of them experiences a terrifying transformation. The excursion was going great until Mel decided to go skinny-dipping in a nearby basin, and emerges bloodied and confused. Later, when Mel starts to sprout razor sharp teeth and appears to turn rabid, her friends become the prey in a vicious, bloody hunt. Before long yet another one of them begins showing signs of infection, prompting the rest of the group to fight for their lives with everything they've got. Retreating into a cave as a last, desperate measure, the remaining survivors discover that the mysterious painting they came to study could hold the secret to the horrifying curse.     Source: allmovie.com