It's not dangerous, according to the Guam Environmental Protection Agency. If you were in Tumon Bay this weekend, you may have noticed a reddish-brown discoloration in the waters.

After receiving photos of the strange occurrence, Guam EPA's Environmental Monitoring and Analytical Services conducted a shoreline assessment. They determined the discolored waters were a result of red tide. Red tides are caused by an abundance of microorganisms called dinoflagellates, according to a release. 

For most people, red tides aren't harmful, according to Guam EPA. However, people with skin allergies could be susceptible to skin and eye irritation if coming into contact with it.

The last reported red tide sighting in Tumon Bay was on July 6, 2017, according to Guam EPA Public Information Officer Nic Rupley Lee.