Officials at Cherry Creek Reservoir in Aurora are warning people about toxic blue-green algae, which can cause rashes, gastrointestinal issues, muscle weakness, or even vomiting.

Friends Sonya Dominguez and Vanessa Saenz spent their Sunday morning paddleboarding in the reservoir.

"It was cold today, but it felt really good because it's so hot," said Dominguez. "There was a lot of, like, you know, motorboats out too. So sometimes there would be some waves, which is nice."

They weren't the only ones. Plenty of people took advantage of the long weekend to take a refreshing dip in the water. But the park wasn't full, which surprised them.

"I was surprised. Especially with it being like 4th of July weekend, it was not as busy," Saenz said.

"Yeah, I was anticipating a lot worse, to be honest," Dominguez added.

It may have been because of the blue-green algae on the shore and in the water. Cherry Creek State Park posted online Saturday that the lake has blue-green algae. They advised keeping children and pets out of the water because it can cause illness.

If you come in contact with it, health experts advise showering immediately. You can fish, but park officials urge people to rinse off their fish and dispose of their guts when cleaning them.

Boating is allowed, but they say if you choose to swim, you're doing so at your own risk.

"I was freaking out a little bit about it. I was like, 'it's touching my leg,'" said Saenz.

"I'm really trying to find different places to get in the water because of that," Dominguez said.

Dominguez and Saenz say the algae won't stop them from paddle boarding the rest of the day, but they will make sure not to skip that post-paddle shower they were each planning to take.

"It is what it is," Dominguez said. "We've already been in the water, so might as well just keep it going."

If you have any questions, you can call the park office at 303-690-1166 ext. 1.