When the Coast Guard determines a boat is in distress, resources are sent immediately if possible, even if commercial towing boats or other vessels are assisting. The standard response is an Urgent Marine Information Broadcast, a boat and sometimes an aircraft, Pagels said.

Coast GuardRescue operations sometimes involve swimmers dropped from aircraft, who approach the vessel from the water.

"Those are the three basic components of how to respond to search and rescue and they kind of all happen at once," Pagels said.

When the degree of danger to people or property is in doubt, the agency generally responds as it would to a distress call. Non-distress calls, however, do not necessarily merit an immediate mobilization. In fact, they may not garner a response at all.

Instead, the agency may help boaters contact some other organization or private company for help. The Coast Guard can also put out a Marine Assistance Request Broadcast–a MARB, in Guard parlance–in an attempt to garner assistance from other vessels.

Glen JusticeBelow, pieces of wood and rigging were all that was left of a ketch after 18-knot winds and waves up to 6 feet pounded the boat into a sea wall on Lake Pontchartrain (above). Glen Justice

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Even if the Coast Guard does mobilize, they may not always comply with requests made by the distressed vessel. One case on Lake Pontchartrain in Louisiana illustrates the point well.

On April 6, a 45-foot wooden ketch sailed too close to the sea wall that bounds the lake and could not tack out. The boat ran aground, with waves as high as six feet and 18-knot winds carrying it toward the wall. The boat's owner could not be reached for comment, but witnesses and others involved in the case described a frantic scene.

"When I got out there, the vessel was already on the seawall and the Coast Guard had not showed up yet," said Philip Hubbell, a 56-year-old New Orleans resident who witnessed the rescue. "The waves were extremely steep and large and the boat was pounding on the serrated concrete."

A Coast Guard boat responded soon thereafter, but would not tow the boat off the wall. Agency officials say responses involving the sea wall are a judgment call. Lieutenant Tom Sanborn, a Coast Guard spokesman, said they generally do not tow if the vessel is hard aground or on top of the wall.

"That's not our job," he said, adding that the Guard does not do salvage, but would pull a vessel away from the seawall if doing so would not endanger men or equipment.

Lieutenant Commander Cheri Ben-Iesau, who works for the Coast Guard in New Orleans, gave a similar explanation. "We do not tow," she said. "You can call a commercial salver but the Coast Guard does not tow unless you're going to die if we don't."