Waters turning to blood? Algal bloom turns parts of Sea of Galilee brilliant red

Recently, observers of the Sea of Galilee have noticed the appearance of bright red spots within the waters of the lake, which is also suffering a dramatic drop in level due to the exceedingly dry winter of 2024-2025. 

According to the Israel Water Authority, the red spots are not a cause for concern to swimmers, and are caused by algae in the waters. The Water Authority explained that the red color comes from a pigment produced by the green algae called Botryococcus braunii, and occurs when the algae is exposed to strong sunlight for extended periods. 

The Sea of Galilee turned red: A natural phenomenon caused the formation of spots in the waters of the Sea of Galilee, with no danger to swimmers. The red color results from the accumulation of a natural pigment produced by a certain type of algae, in response to strong sun… pic.twitter.com/NI4nXdmPhZ

— Adi 🎗 (@Adi13) August 4, 2025

The authority assured bathers that this is a well-known phenomenon that has occurred in the past during summer seasons, and does not pose a danger to public health. The Water Authority reiterated that the pigment is not toxic, and no known allergic reactions have been reported during previous occurrences of the phenomenon. 

“Professional tests conducted by researchers at the Sea of Galilee Research Laboratory did not reveal any findings indicating any danger to bathers,” the Water Authority said in a statement. “Furthermore, no allergic reactions have been reported at sites where the algae has appeared in the past.” 

“The Water Authority continues to monitor and continuously monitor the water quality and the ecosystem in the lake, to ensure all uses of the Sea of Galilee, Israel's national lake,” it said. 

The appearance of the bright red pigment was startling for many Israelis vacationing at the popular swimming spot during the summer break. For many, it brought to mind the story of the waters turning to blood in the Exodus story, and for Christians, it also recalled the passage in Revelation 16:4, where it is one of the plagues mentioned in the Bowl Plagues. 

The intense heat over this summer, especially due to the recent heat wave, and following a dry winter, has brought the Sea of Galilee to a low not seen for many years. The water level has been receding at a rate of one centimeter per day in recent weeks.

The water surface level at the Sea of Galilee was listed at -212.47 meters (about 695 feet), just 53 centimeters (21 inches) above the critical -213 meter-line which indicates a dangerously low level that could damage the lake's ecological stability. [The Sea of Galilee sits below sea level, so the water level is measured in negative numbers.] 

Recently, the National Water Carrier to the Sea of Galilee briefly activated the reverse water carrier which pumps desalinated water into the Sea of Galilee. The project is expected to begin full operation in October, as experts are predicting another dry winter.