SYDNEY (Reuters) - A Great White Shark has gatecrashed a tuna research project in Australia, mysteriously appearing inside a fishing pen containing around 100 tuna. The 13-foot shark, weighing about 1,500 pounds, is thought to have either bitten its way into the tuna pond or leapt a 7.5 foot electrified fence while chasing a seal last Thursday. Scientists at the pen off the coast of the South Australian tuna fishing town of Port Lincoln said Tuesday the shark had swum contently around the pen, but they were not sure how the tuna felt about their uninvited guest. A head count...