By Mindy Weisberger, Senior Writer | July 20, 2017 07:10am ET

Credit: Sea-Mer Association

Take a stroll on a beach and you're likely to encounter plentiful evidence of life from the ocean amid the flotsam: stray clumps of seaweed, colorful seashells, even the occasional crustacean or jellyfish.

But sometimes what washes up on a beach is much harder to identify. Perhaps the object is partly decomposed, or represents a species of marine animal or plant rarely glimpsed on land. Or maybe its condition raises questions about previously unknown relationships or behaviors of ocean creatures, or offers hints about unusual ocean dynamics.

Here are some intriguing examples of mysterious and peculiar emissaries from the sea, which remind us that there is much to be discovered about life in the oceans' depths.

Credit: Sea-Mer Association

Qu'est-ce-que c'est? Beginning on July 14, several French beaches in the north of the country experienced a new type of visitor thousands of yellow, clumpy masses that arrived with the tide and defied identification, though reports indicated that they smelled faintly of paraffin.

An estimated several tons of the waxy objects were observed on shores and along 37 miles (60 kilometers) of French coastline, and they might represent a by-product of hot grease in boat exhaust, according to the organization Sea-Mer Association, which is supervising the clean-up.

Credit: Hilarie Sorensen/University of Oregon

Gelatinous, translucent, bumpy-skinned oblong sea creatures called pyrosomes have recently taken up residence in waters along the Pacific coastline of the U.S., congregating in the millions and washing up on beaches and no one knows why.

The so-called "sea pickles" are generally found in more tropical waters, and it is uncertain what triggered their unusual population explosion in 2017, representatives of the National Oceanic and Atmospheric Association said in a statement.

Credit: Patasiwa Kumbang Amalatu/YouTube

Gooey masses of decomposing flesh that wash up on beaches can be particularly challenging to identify. In May, residents of Seram Island, Indonesia were treated to the sight of a beached boat-sized creature dripping with red fluid and with parts of its body inflated by quantities gas-producing bacteria.

However, scientists explained that the creature was a type of baleen whale, pointing out noticeable grooves in its head area and the presence of visible plates that once held rows of brushy baleen filters.

Credit: Leda Olmstead

Hefty ice spheres as big as basketballs and weighing as much as 50 pounds (22 kilograms) clustered along the northeastern coast of Lake Michigan in 2013.

Ice balls like these begin as bits of slush and ice crystals, shaped by the rolling motion of waves close to shore. They are commonly glimpsed in the area during the winter months, but they rarely grow this large, according to Tom Ulrich, deputy superintendent for the park where the icy lumps were found.

Credit: Marine Dynamics

A series of gruesome marine "crime scenes" played out on South African beaches in May and June, when scientists discovered the ragged remains of four great white sharks that were missing their livers.

Orcas emerged as the prime suspects, as they are known to occasionally prey on great whites, and livers along with other internal organs are a "sweet spot" for predators, a marine biologist told Live Science.

Credit: Tyler Dvorak/Catalina Island Conservancy

When a deep-sea oarfish measuring 13.5 feet (4 meters) in length washed up on Catalina Island in California on June 1, 2015, it offered scientists the rare opportunity to take a closer look at the elusive fish's biology.

Because oarfish live in ocean depths, there is much about their anatomy and behavior that is unknown, and teams of scientists jumped at the chance to study the animal's skeleton, muscles, feeding structures and reproductive system which included 7-foot-long ovaries.

Credit: Illustration courtesy of PLOS ONE, modified by the Burke Museum

Part of an 80-million-year-old fossil thighbone found embedded in marine rock in Washington's San Juan islands provided the first evidence that dinosaurs once roamed the state.

Paleontologists discovered the femur while looking for fossilized signs of other extinct animals, and the rock was so hard that it took an entire day to pry the fossil out. Though it is unclear what species of dinosaur the bone belonged to, the scientists eventually identified it as a theropod a type of meat-eating dinosaur in a study published in 2015 in the journal PLOS ONE.

Credit: M. Sid Kelly, YouTube screenshot

In 2014, beachgoers on the western coast of the United States were confronted by millions of squishy blue animals resembling jellyfish but each was topped with a rigid structure resembling a sail.

Each of these tiny organisms, called "by-the-wind sailors," measurs about 2.75 inches (7 centimeters) in length. They typically inhabit the open ocean, preferring warm waters in locations around the world. But every few years, storm activity can sweep them toward coastal regions, where they pile up on beaches in enormous quantities in 2009 or 2010, dead and dying sailors accumulated on a California beach to a depth of several feet, an oceanographer told Live Science in 2014.

Credit: Greg Rouse

On July 13, a Reddit user shared photos of a peculiar, lumpy object on a California beach that resembled "an organ," according to the photographer.

Images of the fleshy object, which was estimated to be 5 inches (13 centimeters) in length showed bulbous purplish regions likely its protruding gut on a partly-decomposed body bisected by a long furrow, with black markings along one side. The puzzling creature's identity was difficult to pinpoint, and marine biologists told Live Science that it could be a type of sea slug (pictured here) or a limpet.

Credit: Proteccin Civil y Bomberos de Acapulco

Perplexed officials and bystanders in Mexico were stymied by a massive, shapeless jumble of pulpy, greyish flesh in 2016, after it washed ashore on an Acapulco beach.

With a little imagination, the remains could perhaps be attributed to a fantastic sea monster. But experts explained that mystery masses such as this one are the decaying heads of sperm whales, made of deflated flesh from the upper part of the head and the mass of connective tissue known as "the junk," from the lower part of the head.

Credit: Bardocz Peter | Shutterstock.com

A beach in Siberia was recently blanketed by something unexpected scores of orb-like snowballs in sizes ranging from that of a tennis ball to nearly 3 feet (1 meter) in diameter.

Local news reports described the balls first appearing on the ice-covered beach in late October, with the spheres shaped by winds and the movement of the tides. Though this is a natural phenomenon, it is quite rare, with long-time residents in the area reporting that they had never seen it before.

Credit: Enrique Talledo, http://www.enriquetalledo.com

Enormous squids that dwell in the deep ocean are rarely seen by people unless they happen to die and wash up on land, as did a giant squid (Architeuthis dux), the largest known invertebrate, in 2013.

The sizable beast beached in October at the La Arena beach in Cantabria, Spain; it measured 30 feet (9 meters) in length and weighed a staggering 400 pounds (180 kilograms).

Credit: Nicole Haroutunian, photo courtesy of Underwater New York.

The organization Underwater New York, a digital multimedia art journal, features works inspired by unusual objects that wash up on shores and lurk in the depths of waterways around New York City.

One of its recently documented finds a lonely mechanical hand with articulated fingers was spotted on the shore of Great Kills Park Beach, in Staten Island. Other peculiar submerged discoveries mentioned by the journal include a grand piano and dead giraffe, both of which were found in Lower New York Bay.

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Mindy Weisberger is a senior writer for Live Science covering general science topics, especially those relating to brains, bodies, and behaviors in humans and other animals living and extinct. Mindy studied filmmaking at Columbia University; her videos about dinosaurs, biodiversity, human origins, evolution, and astrophysics appear in the American Museum of Natural History, on YouTube, and in museums and science centers worldwide. Follow Mindy on Twitter.

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13 Bizarre Things That Washed Up on Beaches - Live Science