'Sea snot' is a collection of mucus-like organic matter found in the sea.
The creamy, jelly-like substance is generally not harmful, but can attract viruses and bacteria, and can become a blanket that suffocates the marine life below.
A large blanket of 'sea snot' has recently spread through the Sea of Marmara, south of Istanbul. It's growth is a result of prolonged warm temperatures and calm weather with abundant nutrients in the water. Balnkets of 'sea snot' can be a large as 200 km (125 miles) across.
Sea snot was first reported in 1729, but outbreaks are far more common now, partly due to climate change.
Read more about the Turkish 'sea snot' blanket at Atlas Obscura
8th June is World Oceans Day - read more at the UN World Oceans Day website