You were in a boat on the way to an oil rig for your mission when your boat went under attack and you were shot in the shoulder and fell off the boat. You blacked out and thought it was the end.

You wake up on a deserted island. It seems desolate, like you're the only person there. Then you see a splash in the water and see a man.

A merman. He quickly ducks back into the water when he sees he's been spotted. He must have saved you and dragged you out the water and onto the island.