"We deeply apologize for any misunderstanding, as it was absolutely not our intent to offend anyone," the American Red Cross said in a statement.
"We're committed to diversity and inclusion in everything that we do," said William Fortune, a regional communications specialist at the Red Cross.
The organization told NBC News that it discontinued production of the poster and removed it from mobile and web platforms.
The poster came under fire after pool patrons noticed the illustration of a pool scene with "super racist" undertones.
"Hey, (American Red Cross), send a new pool poster… (because) the current one... is super racist," John Sawyer wrote on Twitter.
The illustration, titled "Be cool, follow the rules," identifies acceptable and unacceptable behavior at a pool setting. In the drawing, children of color are shown committing infractions while white children are shown acting "cool," or exhibiting appropriate behavior.
The "not cool" actions include a black girl pushing another girl into the water, a black boy diving into the water and another black boy gasping for air.
Margaret Sawyer, the former executive director of the Mixteco/Indigena Community Organizing Project, which aids the indigenous community in Ventura County, California, said she first saw the poster at a pool in Salida, Colorado.
"I thought, 'It must be really outdated. This can't possibly be a recent poster,'" she said.
But then she saw the same poster at a pool in Fort Morgan, Colorado.
"I felt really angry," she said.
"Staff at both of these city pools had never noticed anything wrong with this poster," Sawyer wrote on Facebook. "(It's) horrifying that children across the country are absorbing this message."
We've seen this racist poster twice now in the town pools of Salida and Fort Morgan, Colorado. It is from the Red Cross...
"I just kept staring at it and thinking, 'It looks they're trying to do something here that shows all kids together, of all different backgrounds, but they're clearly not hitting the mark," Sawyer told KUSA.
The Red Cross offered an extended apology:
"The American Red Cross appreciates and is sensitive to the concerns raised regarding one of the water safety posters we produced. We deeply apologize for any misunderstanding, as it was absolutely not our intent to offend anyone. As one of the nation's oldest and largest humanitarian organizations, we are committed to diversity and inclusion in all that we do, every day.
"Going forward, we are developing more appropriate materials that are more representative of our workforce and the communities we serve. Our aquatic instructors have been notified of these concerns and we will advocate that our aquatic partner facilities remove the poster until revised materials are available."
The organization said it is "currently in the process of completing a formal agreement with a diversity advocacy organization for (its) guidance moving forward," The Washington Post reported.
Black Kids Swim, an online resource for African-American families involved in swimming, and KUSA allege that the posters have been in use since 2014, the New York Daily News reported.
"When I saw the poster, I just, was just very saddened that the Red Cross had chosen to put out an image that might... discourage African-Americans from trying swimming if they were new to it, and also something that would extend a negative stereotype," said Ebony Rosemond, director of Black Kids Swim. "How can an organization that prides itself on being so open-minded, so understanding of the diverse populations of the world, create something like this?"
"I'm just a citizen, I'm not an organization, but I would want the Red Cross to collaborate and build relationships with Black Kids Swim and other organizations that do advocacy around this so that this doesn't happen again," said Sawyer. "Clearly, they're thinking of themselves as only having one constituency, and that's not true."