SHIPWRECKED: The U.S. Coast Guard found boating accident survivor Nick Schuyler yesterday on the overturned vessel in the Gulf of Mexico.
COAST GUARD/ADAM CAMPBELL

The U.S. Coast Guard today announced that it had suspended its search at 6:30 P.M. EST for three boaters, including two pro football players, missing in the Gulf of Mexico off the coast of Clearwater, Fla. The trio was part of a group of four men who left from Clearwater on a fishing trip Saturday and were reported missing early Sunday after failing to return. In calling off the hunt, Coast Guard Capt. Timothy Close said that "We're extremely confident that if there are any survivors on the surface of the water that we would have found them," the Associated Press reports.

The missing men are Oakland Raiders linebacker Marquis Cooper, 26, Detroit Lions defensive end Corey Smith, 29, and Will Bleakley, 25, a former tight end at the University of South Florida.

The Coast Guard located their capsized, 21-foot (6.4-meter) Everglades boat along with one survivor about 35 miles (55 kilometers) from the shoreline yesterday afternoon. Former University of South Florida football player Nick Schuyler, 24, found wearing a life vest and clinging to the outboard motor on the overturned vessel, said that he and his friends were pulling up anchor when a large wave rolled over their craft on Saturday, according to the Chicago Tribune. The Coast Guard had initially searched an area of about 16,000 square miles (41,440 square kilometers), but narrowed it to 4,700 square miles (12,170 square kilometers) based on information from Schuyler.

To find out how authorities go about finding those lost at sea or in other vast waters, ScientificAmerican.com spoke with Art Allen, a physical oceanographer with the U.S. Coast Guard Office of Search and Rescue in Washington, D.C.

[An edited transcript of the interview follows]

What's the first thing the Coast Guard does when alerted that someone or something is lost at sea?
The initial step is to talk with the reporting source and essentially gather as much information as possible about the particular case. We want to know possibly where and when the boaters got in trouble, when they left port, where they intended to go fishing and where else they may have gone fishing – what their plan B was. We’d also want to know what boat they were in and what survival gear they had.  We basically determine all the possible scenarios about the incident and establish what it is that that we’re looking for.

How does the Coast Guard use this information to determine where and how to search?
Two years ago, the Coast Guard put a new search planning software into some of its computers called the Search and Rescue Optimal Planning System (SAROPS). It’s the tool they’re using down in Florida to coordinate and determine the optimal plan for this search. SAROPS simulates the drift trajectory for search objects. Over the past 20 years, I’ve done experiments on how stuff drifts in the water, from people to life rafts to 55-gallon oil drums, which all have different drift and detection characteristics.  We take the information we get from the reporting sources and build a case using the SAROPS software – I’ll make one here on my computer as we talk. I was actually just looking at wind and weather off Clearwater where the boaters have gone missing.

How does the software program work?
To begin devising the search in SAROPS, we first pick from a list of search objects for which we have previously calculated drift equations. Looking at types of vessels, we have things like life rafts, sea kayaks, sailboats, skiffs, Cuban refugee rafts, debris-like objects and more. We have a sport boat with a center console as an option, which is what went missing in Florida, so we’ll choose that.

SAROPS is a Monte Carlo-based system that uses thousands of simulations or replications, or “particles,” if you will. Some particles will be assigned as people in the water and others as the boat, and they all can start drifting at different times and locales. What this allows us to do statistically is actually make something like 10,000 guesses about where the boaters got in trouble and when and where they might end up. We can make 10,000 guesses for a given scenario A, and 10,000 guesses for a different scenario B. All these particles get their own weighting as to which scenario is most probable. There’s always uncertainty, of course, which is why we’re having a search in the first place.

Are winds factored into the search parameters?
Yes. Once we have the basics set up, the next step is to get the environmental data that’s required to track these objects. We need wind data over the area of interest through the time of the incident, and not just until now, but also forecasting into the future. If I’m sitting at my desk at 10:30 A.M., say, I’m probably planning the 12 P.M. – 3 P.M. helicopter flight. I need to know winds from last Saturday when the accident happened to this afternoon to know where survivors may have drifted in the intervening four days.