Olympic champion Michael Phelps has announced his intention to retire after the London Olympics.
This undated image released by Discovery Channel shows a great white shark. The channel's annual Shark Week will include requests to support Oceana, an advocacy group focused on ocean conservation. Shark Week's opening lineup Sunday includes "Phelps vs. Shark: Great Gold vs. Great White," with Olympian Michael Phelps testing his speed against that of a great white shark. (Discovery Channel via AP)