A composite image of a pyrosome (Pyrosoma sp.) in daylight (top) and glowing under its own light (bottom) - Florida Straits, USA.

This Pyrosome, genus Pyrosoma, is a free-floating colony of tunicates. Many species are bioluminescent and can glow for extended periods of time. Most pyrosomes are less than a foot in length but several species grow to longer lengths – reaching 60 feet in one species. This specimen was photographed in the Florida Straits, July 2016 but is also common in the Gulf of Mexico.