When the Deepwater Horizon offshore drilling rig exploded in the Gulf of Mexico April 20, it caused the largest offshore oil spill in U.S. history — 1 million to 2 million barrels of oil and counting.

Now, more than two months later, environmental experts, government officials, BP executives and others are still trying to sort out what happened and pick up the pieces. One thing is clear: Aquatics professionals in the Gulf region are on the front lines and, for some, it may be a long, oily summer. Because oil in water can release toxic chemicals harmful to wildlife and humans, authorities have prohibited swimming as far as Alabama and Mississippi. But those beaches remain open for strolling and sunbathing, even if they’re fouled with tarballs and other residue. Weather and other variables will determine where the oil slicks ultimately land. Some doomsday scenarios predict it fouling waters all along the East Coast. Meanwhile, endless images of oily waters and beaches play on the nightly news.

The Gulf Shores are typically known for fine, powdery white sand and calm, clear waters. But that was not the case last month at a number of beaches, including Orange Beach, Ala. The double red flags were flying, meaning it was illegal for anyone to enter the water.

“We have lifeguards on the beach asking people to get out of the water,” said Melvin Shepard, city aquatics coordinator. “We had to cancel a sailing program and a scuba program, which was to go into the Gulf for the first time this year.”

Shepard noted that the normally pristine sand now has a brownish-red tint, and the typically busy beaches are much less crowded.

Indeed, without swimming, many Gulf Coast beach communities are likely to experience a decrease in visitors this summer. And fear could keep people away longer than that. One indicator shows that since the oil spill, group lodging cancellations at Gulf area hotels have increased as much as 25 percent, according to a June survey by the Knowland Group, a leading data firm for the global meetings and conventions industry.

The news seems better in Florida, where less than 1 percent of beaches have been closed — so far, according to Dr. Stephen P. Leatherman, director of The Laboratory for Coastal Research at Florida International University in Miami.

“There’s a perception that the whole Gulf is a tarball. Fishing has been quite curtailed, but so far the [Florida] beaches have done very well compared to what it could be,” Leatherman said, adding that Florida tourism and fishing amounts to $526 billion a year.

The oil spill is affecting pools, too. With fewer beaches, more people are likely to head to their local aquatics facilities to cool off. Shepard has already seen that phenomenon at the pool he operates. However, all that foot traffic could cause overcrowding and pose other problems.

The Centers for Disease Control and Prevention reported at least one e-mail requesting recommendations on how to remove oil from commercial swimming pools. Apparently, people walking on oily beaches are picking up residue as they come in contact with tarballs. When those contaminated individuals jump into pools, they’re tracking in that residue.

Rich Martin, business manager of the Recreational Water Program, NSF International, offers this advice: “In general, if it sinks to the bottom, vacuum it out of the pool into a separate catch/containment. Get it out of the water- and treatment stream fast, and try to avoid sending this muck into the filters.

"Automatic pool-bottom cleaners with the attached catch bags may work to pick up the ¼-inch to ½-inch oil/dirt blobs and keep from sending it to the filters," Martin stated. "But if they are in suspension … old-fashioned manual skimming may be involved.”

Ultimately, he added, officials will need to know which chemicals were used as spill dispersants so they can develop further treatment recommendations.