From brown and mahogany tides to slick surface masses of blue-green scum, stretches of unnaturally abundant algae drift through the Chesapeake Bay. Some of the more benign blooms merely produce foul odors. Others form sweeping masses that block sunlight from reaching the submerged seagrass that provides a habitat for young fish and crabs.

Megan Brubaker dove into the Choptank River in Cambridge for the ChesapeakeMan Ultra Distance Triathlon last month, well aware of the high levels of pollution in the bay, but with no concerns for her health.

Unlike Brubaker, some Maryland residents are terrified at the prospect of swimming in the Chesapeake Bay. But scientists and regular bay swimmers assure there are little to no negative side effects of taking a dip in the water -- as long as you do it at the right time.

When John Smith traveled the bay 400 years ago, he wrote that oysters, "lay as thick as stones," and that sturgeon were plentiful -- "more than could be devoured by dog or man."