Beneath the Ocean Blanket

We live most of our life on the mainland. Modern Florida has 8,500 miles of tidal shoreline. Our ancient story is interwoven with all that fabulous water.  The magic of that long ago time is found in the beautifully sculpted seashells. What a marvel of color and shape lived beneath those coastal inland seas!

The map above shows the central crest of Florida as an island separated from the rest of North America by the Suwannee Strait. Above the tides, the age of mammals flowered with an amazing variety. Some of those animals came to the insular world of Florida.

About 25 million years ago, Florida was bumped north by the Caribbean plate to our south. That little bump caused Florida to bulge along the middle crest and to its west. Today we call the western bulge the Brooksville Crest. At the same time the southern Appalachian Mountains seemed to have grown too. That rise sent sand swirling down the rivers.

Over the years the Suwannee Strait filled with sand flowing from the north.

Carcharodon megalodon sharks grew to fifty feet in length in those ancient oceans. They were the relative of our modern White shark. 

A student of paleontology, Brian Ridgway, believed he found evidence for the drama to the left in the what was known as the Toy Town landfill in North St. Petersburg. He found a partial skeleton of a whale with the teeth of this giant shark embedded in its ribs.

In truth, we may never know what Florida really looked like when the ancient seas covered much of it. Using the evidence available, I have drawn the map to the right.

Right is an image of central Florida. The islands sticking out on the left will form Tampa Bay. We are looking for a site, a little south, in what is now northeast Sarasota.

Map of Florida about 70,000 BPE.

What a wonder that prehistoric ocean floor would have offered.

This is an easy dive at only about 8 or 9 feet deep at high tide. We’re opposite the lee side of a sand bar which almost reaches the surface. To the west of us are the barrier islands that protect the mainland. 

The ocean bottom is covered with worm shells. You can’t see the shells because they are covered by a thin layer of sand. What you see is the delicate feathery fans they send up to filter out small creatures from the passing water.


Tiny fish dart around the feathers. When a starfish comes close, the tendrils withdraw beneath the sand. Scallops, the size of saucers, litter the bottom. Their brightly colored tentacles, waving food into their shells, are punctuated with dark metallic blue eyespots. A variety of other small clams make this place their home as well.

That’s what these snails are all about. They’re hunters. Their teeth are part of a strange sawing kind of syst

em called a radula. The radula turns back and forth creating a perfectly round hole in the shell of the shellfish it’s eating.

Tip yourself up for a moment to see above the waves. We’re heading for those islands to the east. Th

e bottom drops away . Eel grass will thin into patches. Finally, the velvet rays of sunlight, dancing down, display patterns on a sandy bottom. It almost looks like a desert with cloud shadows passing by. Here and there we see the holes made by a comical small fish. It’s a blenny. It has a short face with large eyes and it hovers just outside its borough. If any other blenny comes around, it chases it away. Clams live beneath the sand and moon snails hunt them. The extinct Murex (left) hunted there also.

Climbing up toward the surface reveals beds of stingray’s. Arrow crabs, scurry over the rippled bottom, looking for morsels. They haven’t changed in many millions of years.

The wave motion tumbles shells into a hash. Broken halves litter the bottom in a mosaic of fantastic colors. The ribbons of sunlight dazzle this kaleidoscopic palette with sweeping rhythms.

On the other side of the barrier island is a whole new symphony of life. But, for us, other times whisper in the winds which ruffle the surface of the Gulf.

We’re looking for a shallow place, just off the coast, where an amazing variety of beautiful shells existed.

Central Gulf Coast about 7,000 BPE.

Although plenty of sharks still hunt these waters, the really big one, Carcharodon megalodon, has already gone extinct. But it’s still a good idea to be careful!

This beautiful shell is called Vassum horridum. If it had a color, it faded long ago. No one has ever seen a living one. To me, it’s a marvel of shape.
Those spines were designed to keep other snails from drilling a hole into the shell and eating it. As you can see, it didn’t work. A snail climbed on this shell’s back and drilled that hole in its center. But this vasum does the same thing to other shellfish.
And, that’s what seashells are all about. Their wonderful shells are body armor for the creatures that live inside them.


Crown conchs lived at the same time and while the Vasum went extinct, Crown conchs still survive in the estuaries of modern Florida. How that works remains an unanswered question.

Like life on land, the animals beneath the sea live in very distinct environmental systems. You can look at it from the ocean to the land, or from the land to the ocean. The path goes either way and is wonderfully exciting.

When you jump into the ocean with your snorkle and fins, the images at first are a confusion of sights. It’s like landing in the middle of an unknown forest. What you usually see is the single environmental system which surrounds you.