Many Americans were unaware of who they were or what they did until this year. But when Hurricane Katrina hit and the waters began to rise, U.S. Coast Guard members moved in by air and by sea, risking their lives to save thousands of others.
"When we flew into the storm the winds were still pretty high," said Petty Officer Joel Sayers, a Coast Guard rescue swimmer. "You're always expecting to see one or two people here or there that you could actually hoist and move out of harm's way, but it was true devastation. The water was already up over the roofs of some houses, and it was still rising. There were people everywhere, holding on to trees, people on top of their homes, people trying to climb on top of their homes."
The Coast Guard rescue swimmers were some of the first on the scene in Louisiana and Mississippi, rescuing victims before the storm had even passed.
Sayers says during that first 24 hours, the rescue teams were running on adrenaline.
"As many as you can get as fast as you could pick them up and as safely as you could do it," he said.
More than 5,000 Coast Guard personnel conducted rescue operations, using 62 aircraft and 131 cutters and small boats as they lived up to the motto Semper Paratus, or Always Ready.
"I think the Coast Guard's efforts are always tremendous," Sayers said. "I think in this particular situation, I think they went way beyond what anybody expected any agency to do."
It was a mission for which they had never trained. Normally, the Coast Guard saves an average of 5,500 people a year. Within two weeks of Katrina, it had rescued or evacuated more than 33,000 people under the most difficult circumstances imaginable.
"I found that it was one of the hardest situations and some of the hardest rescues ever," said Sayers. "You constantly think about everything around you -- the power lines, the trees, the broken gas lines, the amount of things floating in the water, the roofs separating. There were so many different hazards out there it was hard to focus on one thing. You constantly had to keep your head on a swivel."
And those images will be with them forever.
"You look at the crew members that are around you, your fellow Coasties, and you wonder if they're OK," Sayers said. "It's a lot to take in. It's a lot to carry with you. I will always remember Katrina. It will always be a part of my heart and will always be a part of my soul."
ABC News' Bob Woodruff filed this report for "World News Tonight."