As reported by CNN, a pod of dolphins surrounded some lifeguards off the New Zealand coast.  The four swimmers were herded together by the dolphins--initially worrying the swimmers until one of them saw the  9 foot long Great White shark.  The dolphins circled the swimmers for forty minutes, until the danger apparently passed.

UPDATE: According to to The Scotsman, two of the pod of dolphins that saved the swimmers are believed to have been killed by poachers.