The story of how the starfish got its arms reminds us that even animals that might be familiar to us today can have incredibly deep histories - ones that stretch back almost half a billion years.

The biggest (and most mysterious!) migration in the world happens every night in the ocean as 10 billion tons of zooplankton swim to the surface to feed. This undersea journey is known as Diel vertical migration, and it occurs in every...

From spooky-looking towers that belch white "smoke" to a mountain range in the middle of the Atlantic ocean, the seafloor is full of features as dynamic as the surface! That's part of why we've done many SciShow episodes about the ocean....

Coral reef fish, like the yellow tang surgeonfish, begin life in a fascinating and weird way - as tiny floating larvae! These babies are capable of drifting thousands of miles on ocean currents, far from the reefs where they were born....

Break down the oil slick, keep it off the shores: that's grounds for pumping toxic dispersant into the Gulf, say clean-up overseers. Susan Shaw shows evidence it's sparing some beaches only at devastating cost to the health of the deep sea.

Now you "sea" them, now you don't! Cuttlefish are more than the chameleons of the sea, these cephalopods take camouflage to a whole new level.

We may think of a lot of critters with crab-like body plans as crabs, but, technically, many of them are other types of crustaceans. So why do they share so many physical traits?

You’d never tell just by staring out from a sandy beach, but the coasts are gradually getting darker, and the effects of this darkening are only beginning to be understood.

When the ocean changes, the planet changes -- and it all starts with microbes, says biological oceanographer Angelicque White. Backed by decades of data, White shares how scientists use these ancient microorganisms as a crucial barometer...

About 60 percent of the ocean is a cold, dark region that spans down to 11,000 meters. This zone is known as the deep ocean, and though it seems like an inhospitable and remote corner of the planet, it is actually one of the greatest...

Hamish Jolly, an ocean swimmer in Australia, wanted a wetsuit that would deter a curious shark from mistaking him for a potential source of nourishment. (Which, statistically, is rare, but certainly a fate worth avoiding.) Working with a...

Deep in the ocean, fluffy bits of organic matter fall like snow. But this marine snow isn’t just pretty; it’s an essential part of our ocean food webs and our global climate!

To finish things up with Echinodermata, we will look at class Echinoidea, the sea urchins, and class Holothuroidea, the sea cucumbers. What are these spiny things we call urchins? What is their anatomy like? What the heck is a sea...

Continuing with the invertebrate chordates, we arrive at subphylum Tunicata, also known as the tunicates. There are over 3,000 species within this clade, and the creatures are fascinating. The body of a tunicate is enclosed in a thick...

Howcast - Learn how to fix cloudy tank water from aquarium expert Joseph Caparatta in this Howcast video.

Meet Harbor, the PPG Aquarium's green sea turtle.

At Pittsburgh's PPG Aquarium, this 8-year-old turtle is getting a second chance.

At Pittsburgh's PPG Aquarium, this 8-year-old turtle is getting a second chance.

Hear his story and see what aquarists at Pittsburgh's PPG Aquarium did to give him a fighting chance.

At Pittsburgh's PPG Aquarium, this 8-year-old turtle is getting a second chance.

As of January 2024, the United States grew by about 400,000 square miles of territory or larger than the state of Texas. This was done under a little known United Nations policy called the Extended Continental Shelf. So why has the...

From Mexico all the way up to Alaska, hundreds of gray whales have been washing up ashore. The deaths peaked in 2019, and the numbers were so significant that it led scientists to call it an Unusual Mortality Event (UME) which kicked...

Now that we are familiar with the characteristics of annelids, let's zoom in on the polychaetes, which are the segmented marine worms. What do these worms do in the sea all day long? How are they different from land worms? Let's get a...

We now arrive at the most famous of the mollusks, the cephalopods. These include squids, nautiluses, cuttlefish, and the fascinating octopuses. These creatures are the largest and most intelligent invertebrates on Earth. Let's learn all...