A remote underwater vehicle approaches a rare "tar lily” volcano on the bottom of the Gulf of Mexico. NOAA Okeanos Explorer Program

A bizarre anomaly deep beneath the Gulf of Mexico had researchers holding out for a sunken ship.

But what they discovered on the seafloor more than a mile under the surface wasn’t a shipwreck after all. Scientists from Texas A&M University at Galveston and the National Oceanic and Atmospheric Administration, or NOAA, announced on April 24 that what they first thought was the hull of a sunken vessel was actually two rare tar volcanoes, ocean floor vents that spout asphalt instead of lava, that erupted in the shapes of blooming flowers.

Researchers dubbed the solidified explosions “tar lilies.” Each measured roughly 20 feet across and 10 feet high, according to Fox News.

"It's kind of like Play-Doh being pushed through a mold," one researcher told the Houston Chronicle. "As [the hot asphalt] came out it hit cold water, probably quite rapidly, and fractured in a way that made it splay onto the sea floor like a flower."

Tar volcanoes, or asphalt volcanoes, were first documented in 2003 and have been found along the coasts of the U.S. and Mexico. The domes are made primarily of crude oil, in effect the same stuff used to pave parking lots and highways.

The tar is relatively hot when it comes up from deep reservoirs below the ocean floor, but it hardens when it meets the cold seawater.

“Imagine that this would be like a big piece of molten tar,” William Kiene, a regional scientist with NOAA’s Office of National Marine Sanctuaries, told KHOU. “And as it gets to the surface and it comes in contact with the cold water, it would solidify. So it came up in this very peculiar shape, like a lily.”

The tar lilies were discovered about 150-170 miles off the coast of Texas, near Galveston.

Researchers were initially scanning the seafloor for centuries-old shipwrecks. The team knew of three sunken ships lying off the coast of Galveston, and they had even recovered several artifacts, including anchors, dishes, a clock and jars of ginger that were probably used to treat seasickness, from the wreckage. They thought the tar volcanoes may have been a fourth ship.

Cameras mounted on underwater vehicles showed otherwise.

There were several colonies of various forms of marine life, including coral, anemones and tube worms, on the surface of the tar lilies.