MIAMI – Hallendale Beach, just north of Miami, was awash in palm-sized jellyfish last week, creating the illusion of a blue sandy beach.

Photos of thousands of blue jellyfish washed up onshore have surfaced on social media, some showing them entirely covering parts of the sand.

Fortunately the jellyfish, called Velella velella or “purple sailors,”are considered relatively harmless.

“This happens about every three years. We are flying our Purple flag for dangerous marine life,” city officials posted on Facebook, also mentioning that there could be man o’ war jellyfish among the purple sailors.

“We have had only one minor sting in the first three hours of our day.

Public works beach tractor did rake up numerous [jellyfish], but they continue to wash up and clean up will be a gradual process,” officials said.