Mother dies, father missing on family trip to remote Australian beach- jamie Lerman
A family sets out on a trip of a life time when they decide to go on a trip all along the coastline of Australia. But things go wrong when the family is swimming by the sea and they find the mother lying face down in the water. A witness says they saw the father floating away too and then become submerged in the water. They declared the mother dead and are still in search for the father.

http://www.cnn.com/2013/05/16/world/asia/australia-road-trip-tragedy/index.html?iref=allsearch

This is such a crazy and wild thing to happen. It's not clear if they know the cause of death or if any other similar occurances have happened, but hopefully they can figure out what has been happening.